Add rendering implementation for LWJGL
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package imgui.gl3;
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import imgui.DrawData;
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import imgui.ImGui;
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import imgui.TexDataRGBA32;
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import java.io.*;
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import java.util.Objects;
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import static org.lwjgl.opengl.GL30.*;
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/**
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* This class mostly a straightforward port of the https://raw.githubusercontent.com/ocornut/imgui/v1.74/examples/imgui_impl_opengl3.cpp adapted to Java and LWJGL realms.
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* <p>
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* It do support a backup of the current GL state before rendering and restoring of its initial state after.
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* But some specific state variables may be missed (all which are hidden under '#ifdef' macros in the original imgui file).
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* <p>
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* By default this implementation uses shaders with 130 version of GLSL (OpenGL 3.0).
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* You can provide your own shaders into the {@link ImGuiImplGl3#init(CharSequence, CharSequence)} method.
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*/
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public class ImGuiImplGl3 {
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private int vBufferHandle = 0;
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private int iBufferHandle = 0;
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private boolean isFontInitialized = false;
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// Shader stuff
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private int programId = 0;
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private int fragmentShaderId = 0;
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private int vertexShaderId = 0;
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// Texture used by fonts
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private int gFontTexture = 0;
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// Projection matrix for ImGui
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private final float[] projMatrix = new float[4 * 4];
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// Variables used to backup GL state before and after rendering of ImGui
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private final int[] lastActiveTexture = new int[1];
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private final int[] lastProgram = new int[1];
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private final int[] lastTexture = new int[1];
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private final int[] lastArrayBuffer = new int[1];
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private final int[] lastViewport = new int[4];
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private final int[] lastScissorBox = new int[4];
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private final int[] lastBlendSrcRgb = new int[1];
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private final int[] lastBlendDstRgb = new int[1];
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private final int[] lastBlendSrcAlpha = new int[1];
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private final int[] lastBlendDstAlpha = new int[1];
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private final int[] lastBlendEquationRgb = new int[1];
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private final int[] lastBlendEquationAlpha = new int[1];
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private boolean lastEnableBlend = false;
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private boolean lastEnableCullFace = false;
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private boolean lastEnableDepthTest = false;
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private boolean lastEnableScissorTest = false;
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/**
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* This method SHOULD be called before calling of {@link ImGuiImplGl3#render(DrawData)} method.
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* By using this method shaders with 130 version of GLSL will be used for render.
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*/
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public void init() {
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final CharSequence fragShaderSource = readFromResources("default.frag");
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final CharSequence vertShaderSource = readFromResources("default.vert");
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prepareShader(fragShaderSource, vertShaderSource);
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prepareFont();
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}
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/**
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* This method SHOULD be called before calling of {@link ImGuiImplGl3#render(DrawData)} method.
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*
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* @param fragShaderSource fragment shader to use for render
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* @param vertShaderSource vertex shader to use for render
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*/
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public void init(final CharSequence fragShaderSource, final CharSequence vertShaderSource) {
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prepareShader(fragShaderSource, vertShaderSource);
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prepareFont();
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}
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/**
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* Method which renders {@link DrawData} from ImGui.
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*
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* @param drawData data used to draw ImGui interface to your current OpenGL context
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*/
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public void render(final DrawData drawData) {
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if (drawData.cmdListsCount <= 0) {
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return;
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}
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// Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
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int fbWidth = (int) (drawData.displaySizeX * drawData.framebufferScaleX);
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int fbHeight = (int) (drawData.displaySizeY * drawData.framebufferScaleY);
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if (fbWidth <= 0 || fbHeight <= 0) {
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return;
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}
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if (!isFontInitialized) {
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isFontInitialized = true;
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vBufferHandle = glGenBuffers();
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iBufferHandle = glGenBuffers();
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glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, iBufferHandle);
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glBufferData(GL_ELEMENT_ARRAY_BUFFER, drawData.iByteBuffer.capacity(), GL_STATIC_DRAW);
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glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
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}
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backupGlState();
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bind(drawData);
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int verticesOffset = 0;
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int indexOffset = 0;
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for (int i = 0; i < drawData.cmdListsCount; i++) {
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drawData.vByteBuffer.limit(verticesOffset + 4);
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final int verticesSize = (int) drawData.vByteBuffer.getFloat(verticesOffset);
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drawData.iByteBuffer.limit(indexOffset + 2);
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final short indexSize = drawData.iByteBuffer.getShort(indexOffset);
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final int cmdSize = (int) drawData.cmdByteBuffer.getFloat();
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final int verticesStartOffset = verticesOffset + 4;
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final int indexStartOffset = indexOffset + 2;
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drawData.vByteBuffer.position(verticesStartOffset);
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drawData.iByteBuffer.position(indexStartOffset);
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final int newVlimit = verticesStartOffset + verticesSize * DrawData.vBufferSize;
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final int newIlimit = indexStartOffset + indexSize * DrawData.iBufferSize;
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drawData.vByteBuffer.limit(newVlimit);
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drawData.iByteBuffer.limit(newIlimit);
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glBufferData(GL_ARRAY_BUFFER, drawData.vByteBuffer, GL_STATIC_DRAW);
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glBufferData(GL_ELEMENT_ARRAY_BUFFER, drawData.iByteBuffer, GL_STATIC_DRAW);
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verticesOffset += ((verticesSize) * DrawData.vBufferSize) + 4;
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indexOffset += ((indexSize) * DrawData.iBufferSize) + 2;
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final float clipOffX = drawData.displayPosX; // (0,0) unless using multi-viewports
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final float clipOffY = drawData.displayPosY;
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final float clipScaleX = drawData.framebufferScaleX; // (1,1) unless using retina display which are often (2,2)
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final float clipScaleY = drawData.framebufferScaleY;
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int idxBufferOffset = 0;
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for (int j = 0; j < cmdSize; j++) {
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final int elemCount = (int) drawData.cmdByteBuffer.getFloat();
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float clipRectX = drawData.cmdByteBuffer.getFloat();
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float clipRectY = drawData.cmdByteBuffer.getFloat();
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float clipRectZ = drawData.cmdByteBuffer.getFloat();
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float clipRectW = drawData.cmdByteBuffer.getFloat();
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final int textureID = (int) drawData.cmdByteBuffer.getFloat();
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clipRectX = (clipRectX - clipOffX) * clipScaleX;
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clipRectY = (clipRectY - clipOffY) * clipScaleY;
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clipRectZ = (clipRectZ - clipOffX) * clipScaleX;
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clipRectW = (clipRectW - clipOffY) * clipScaleY;
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if (clipRectX < fbWidth && clipRectY < fbHeight && clipRectZ >= 0.0f && clipRectW >= 0.0f) {
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glScissor((int) clipRectX, (int) (fbHeight - clipRectW), (int) (clipRectZ - clipRectX), (int) (clipRectW - clipRectY));
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glBindTexture(GL_TEXTURE_2D, textureID);
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glDrawElements(GL_TRIANGLES, elemCount, GL_UNSIGNED_SHORT, idxBufferOffset);
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}
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idxBufferOffset += elemCount * 2;
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}
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}
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unbind();
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restoreModifiedGlState();
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}
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/**
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* Call this method in the end of your app working state to clear used resources.
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*/
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public void dispose() {
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glDeleteTextures(gFontTexture);
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glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
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glDeleteBuffers(iBufferHandle);
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glDeleteBuffers(vBufferHandle);
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glDetachShader(programId, vertexShaderId);
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glDetachShader(programId, fragmentShaderId);
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glDeleteProgram(programId);
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}
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private void prepareShader(final CharSequence fragShaderSource, final CharSequence vertShaderSource) {
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fragmentShaderId = loadAndCompileShader(GL_FRAGMENT_SHADER, fragShaderSource);
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vertexShaderId = loadAndCompileShader(GL_VERTEX_SHADER, vertShaderSource);
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programId = glCreateProgram();
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glAttachShader(programId, fragmentShaderId);
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glAttachShader(programId, vertexShaderId);
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glLinkProgram(programId);
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if (glGetProgrami(programId, GL_LINK_STATUS) != GL_TRUE) {
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throw new IllegalStateException(glGetProgramInfoLog(programId));
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}
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}
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private void prepareFont() {
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TexDataRGBA32 texData = new TexDataRGBA32();
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ImGui.GetTexDataAsRGBA32(texData, texData.pixelBuffer);
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gFontTexture = glGenTextures();
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glBindTexture(GL_TEXTURE_2D, gFontTexture);
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
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glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
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glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texData.width, texData.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, texData.pixelBuffer);
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ImGui.SetFontTexID(gFontTexture);
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}
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private void backupGlState() {
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glGetIntegerv(GL_ACTIVE_TEXTURE, lastActiveTexture);
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glGetIntegerv(GL_CURRENT_PROGRAM, lastProgram);
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glGetIntegerv(GL_TEXTURE_BINDING_2D, lastTexture);
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// int[] last_sampler; glGetIntegerv(GL_SAMPLER_BINDING, &last_sampler); // do it by yourself if needed
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glGetIntegerv(GL_ARRAY_BUFFER_BINDING, lastArrayBuffer);
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// int[] last_vertex_array_object; glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array_object); // do it by yourself if needed
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// int[] last_polygon_mode; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode); // do it by yourself if needed
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glGetIntegerv(GL_VIEWPORT, lastViewport);
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glGetIntegerv(GL_SCISSOR_BOX, lastScissorBox);
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glGetIntegerv(GL_BLEND_SRC_RGB, lastBlendSrcRgb);
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glGetIntegerv(GL_BLEND_DST_RGB, lastBlendDstRgb);
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glGetIntegerv(GL_BLEND_SRC_ALPHA, lastBlendSrcAlpha);
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glGetIntegerv(GL_BLEND_DST_ALPHA, lastBlendDstAlpha);
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glGetIntegerv(GL_BLEND_EQUATION_RGB, lastBlendEquationRgb);
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glGetIntegerv(GL_BLEND_EQUATION_ALPHA, lastBlendEquationAlpha);
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lastEnableBlend = glIsEnabled(GL_BLEND);
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lastEnableCullFace = glIsEnabled(GL_CULL_FACE);
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lastEnableDepthTest = glIsEnabled(GL_DEPTH_TEST);
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lastEnableScissorTest = glIsEnabled(GL_SCISSOR_TEST);
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}
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private void restoreModifiedGlState() {
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glUseProgram(lastProgram[0]);
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glBindTexture(GL_TEXTURE_2D, lastTexture[0]);
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glActiveTexture(lastActiveTexture[0]);
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glBindBuffer(GL_ARRAY_BUFFER, lastArrayBuffer[0]);
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glBlendEquationSeparate(lastBlendEquationRgb[0], lastBlendEquationAlpha[0]);
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glBlendFuncSeparate(lastBlendSrcRgb[0], lastBlendDstRgb[0], lastBlendSrcAlpha[0], lastBlendDstAlpha[0]);
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// @formatter:off
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if (lastEnableBlend) glEnable(GL_BLEND); else glDisable(GL_BLEND);
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if (lastEnableCullFace) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE);
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if (lastEnableDepthTest) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST);
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if (lastEnableScissorTest) glEnable(GL_SCISSOR_TEST); else glDisable(GL_SCISSOR_TEST);
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// @formatter:on
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glViewport(lastViewport[0], lastViewport[1], lastViewport[2], lastViewport[3]);
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glScissor(lastScissorBox[0], lastScissorBox[1], lastScissorBox[2], lastScissorBox[3]);
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}
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private void bind(final DrawData drawData) {
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glViewport(0, 0, (int) drawData.displaySizeX, (int) drawData.displaySizeY);
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glActiveTexture(GL_TEXTURE0);
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glEnable(GL_BLEND);
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glBlendEquation(GL_FUNC_ADD);
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glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
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glDisable(GL_CULL_FACE);
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glDisable(GL_DEPTH_TEST);
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glEnable(GL_SCISSOR_TEST);
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final float L = drawData.displayPosX;
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final float R = drawData.displayPosX + drawData.displaySizeX;
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final float T = drawData.displayPosY;
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final float B = drawData.displayPosY + drawData.displaySizeY;
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// Orthographic matrix projection
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projMatrix[0] = 2.0f / (R - L);
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projMatrix[5] = 2.0f / (T - B);
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projMatrix[10] = -1.0f;
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projMatrix[12] = (R + L) / (L - R);
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projMatrix[13] = (T + B) / (B - T);
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projMatrix[15] = 1.0f;
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// Bind vertices
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glBindBuffer(GL_ARRAY_BUFFER, vBufferHandle);
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int location = glGetAttribLocation(programId, "Position");
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glEnableVertexAttribArray(location);
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glVertexAttribPointer(location, 2, GL_FLOAT, false, 20, 0);
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location = glGetAttribLocation(programId, "UV");
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glEnableVertexAttribArray(location);
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glVertexAttribPointer(location, 2, GL_FLOAT, false, 20, 8);
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location = glGetAttribLocation(programId, "Color");
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glEnableVertexAttribArray(location);
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glVertexAttribPointer(location, 4, GL_UNSIGNED_BYTE, true, 20, 16);
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//Bind index
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glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, iBufferHandle);
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// Bind shader
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glUseProgram(programId);
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glUniformMatrix4fv(glGetUniformLocation(programId, "ProjMtx"), false, projMatrix);
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glUniform1i(glGetUniformLocation(programId, "Texture"), 0);
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}
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private void unbind() {
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// Unbind vertices
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glBindBuffer(GL_ARRAY_BUFFER, 0);
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glDisableVertexAttribArray(glGetAttribLocation(programId, "Position"));
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glDisableVertexAttribArray(glGetAttribLocation(programId, "UV"));
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glDisableVertexAttribArray(glGetAttribLocation(programId, "Color"));
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// Unbind index
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glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
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glFlush();
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// Unbind shader
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glUseProgram(0);
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}
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private int loadAndCompileShader(final int type, final CharSequence source) {
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int id = glCreateShader(type);
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glShaderSource(id, source);
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glCompileShader(id);
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if (glGetShaderi(id, GL_COMPILE_STATUS) != GL_TRUE) {
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throw new IllegalStateException(glGetShaderInfoLog(id));
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}
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return id;
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}
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private CharSequence readFromResources(final String path) {
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StringBuilder builder = new StringBuilder();
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try (InputStream in = getClass().getClassLoader().getResourceAsStream(path);
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BufferedReader reader = new BufferedReader(new InputStreamReader(Objects.requireNonNull(in)))) {
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String line;
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while ((line = reader.readLine()) != null) {
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builder.append(line).append('\n');
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}
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} catch (IOException ex) {
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throw new UncheckedIOException("Failed to read from resources!", ex);
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}
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return builder.toString();
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}
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}
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