[API] Added callback binding for InputText (#156)

* Added callback binding for InputText

* Add JavaDoc

* Change

* Add Javadoc

* Fix Import

* Teaks and improvements

- Extended example;
- Added input text callback ImGuiInputTextFlags#CallbackEdit;
- Minor code improvements.

---------

Co-authored-by: SpaiR <klimbetoo@gmail.com>

imgui-binding/src/main/java/imgui/ImGuiInputTextCallbackData.java

@@ -0,0 +1,182 @@
+package imgui;
+
+import imgui.binding.ImGuiStruct;
+
+/**
+ * Shared state of InputText(), passed as an argument to your callback when a ImGuiInputTextFlags_Callback* flag is used.<p>
+ * The callback function should return 0 by default.<p>
+ * Callbacks (follow a flag name and see comments in ImGuiInputTextFlags_ declarations for more details)<p>
+ * - ImGuiInputTextFlags_CallbackEdit:        Callback on buffer edit (note that InputText() already returns true on edit, the callback is useful mainly to manipulate the underlying buffer while focus is active)<p>
+ * - ImGuiInputTextFlags_CallbackAlways:      Callback on each iteration<p>
+ * - ImGuiInputTextFlags_CallbackCompletion:  Callback on pressing TAB<p>
+ * - ImGuiInputTextFlags_CallbackHistory:     Callback on pressing Up/Down arrows<p>
+ * - ImGuiInputTextFlags_CallbackCharFilter:  Callback on character inputs to replace or discard them. Modify 'EventChar' to replace or discard, or return 1 in callback to discard.<p>
+ * - ImGuiInputTextFlags_CallbackResize:      Callback on buffer capacity changes request (beyond 'buf_size' parameter value), allowing the string to grow.<p>
+ */
+public class ImGuiInputTextCallbackData extends ImGuiStruct {
+    public ImGuiInputTextCallbackData(final long ptr) {
+        super(ptr);
+    }
+
+    /*JNI
+        #include "_common.h"
+
+        #define IMGUI_CALLBACK_DATA ((ImGuiInputTextCallbackData*)STRUCT_PTR)
+     */
+
+    /**
+     * One ImGuiInputTextFlags_Callback*
+     *
+     * @return ImGuiInputTextFlags
+     */
+    public native int getEventFlag(); /*
+        return IMGUI_CALLBACK_DATA->EventFlag;
+    */
+
+    /**
+     * What user passed to InputText()
+     *
+     * @return ImGuiInputTextFlags
+     */
+    public native int getFlags(); /*
+        return IMGUI_CALLBACK_DATA->Flags;
+    */
+
+    /**
+     * [CharFilter] Character input;
+     *
+     * @return Character input
+     */
+    public native int getEventChar(); /*
+        return IMGUI_CALLBACK_DATA->EventChar;
+    */
+
+    /**
+     * [CharFilter] Replace character with another one, or set to zero to drop. return 1 is equivalent to setting EventChar=0;
+     *
+     * @param c Replaced characters
+     */
+    public void setEventChar(final char c) {
+        setEventChar((int) c);
+    }
+
+    /**
+     * [CharFilter] Replace character with another one, or set to zero to drop. return 1 is equivalent to setting EventChar=0;
+     *
+     * @param c Replaced characters
+     */
+    public native void setEventChar(int c); /*
+        IMGUI_CALLBACK_DATA->EventChar = c;
+    */
+
+    /**
+     * [Completion,History]
+     *
+     * @return Key pressed (Up/Down/TAB)
+     */
+    public native int getEventKey(); /*
+        return IMGUI_CALLBACK_DATA->EventKey;
+    */
+
+    /**
+     * [Resize] Can replace pointer <p>
+     * [Completion,History,Always] Only write to pointed data, don't replace the actual pointer!
+     *
+     * @return Buf
+     */
+    public native String getBuf(); /*
+        return env->NewStringUTF(IMGUI_CALLBACK_DATA->Buf);
+    */
+
+    /**
+     * Set if you modify Buf/BufTextLen!
+     *
+     * @return Dirty
+     */
+    public native boolean getBufDirty(); /*
+        return IMGUI_CALLBACK_DATA->BufDirty;
+    */
+
+    /**
+     * Set if you modify Buf/BufTextLen!
+     *
+     * @param dirty Dirty
+     */
+    public native void setBufDirty(boolean dirty); /*
+        IMGUI_CALLBACK_DATA->BufDirty = dirty;
+    */
+
+    /**
+     * Current cursor position
+     *
+     * @return Current cursor position
+     */
+    public native int getCursorPos(); /*
+        return IMGUI_CALLBACK_DATA->CursorPos;
+    */
+
+    /**
+     * Set the current cursor position
+     *
+     * @param pos Set the current cursor position
+     */
+    public native void setCursorPos(int pos); /*
+        IMGUI_CALLBACK_DATA->CursorPos = pos;
+    */
+
+    /**
+     * Selection Start
+     *
+     * @return Selection Start
+     */
+    public native int getSelectionStart(); /*
+        return IMGUI_CALLBACK_DATA->SelectionStart;
+    */
+
+    /**
+     * Set Selection Start
+     *
+     * @param pos Selection Start
+     */
+    public native void setSelectionStart(int pos); /*
+        IMGUI_CALLBACK_DATA->SelectionStart = pos;
+    */
+
+    /**
+     * Selection End
+     *
+     * @return Selection End
+     */
+    public native int getSelectionEnd(); /*
+        return IMGUI_CALLBACK_DATA->SelectionEnd;
+    */
+
+    /**
+     * Set Selection End
+     *
+     * @param pos Selection End
+     */
+    public native void setSelectionEnd(int pos); /*
+        IMGUI_CALLBACK_DATA->SelectionEnd = pos;
+    */
+
+    /**
+     * Delete Chars
+     *
+     * @param pos        Start Delete Pos
+     * @param bytesCount Delete Char Count
+     */
+    public native void deleteChars(int pos, int bytesCount); /*
+        IMGUI_CALLBACK_DATA->DeleteChars(pos, bytesCount);
+    */
+
+    /**
+     * Insert Chars
+     *
+     * @param pos insert Psos
+     * @param str insert String
+     */
+    public native void insertChars(int pos, String str); /*
+        IMGUI_CALLBACK_DATA->InsertChars(pos, str);
+    */
+}