InputText: Added support for buffer size/capacity changes via the ImGuiInputTextFlags_CallbackResize flag. (#2006, #1443, #1008).

imgui.h

@@ -643,7 +643,7 @@ enum ImGuiInputTextFlags_
     ImGuiInputTextFlags_CallbackCompletion  = 1 << 6,   // Call user function on pressing TAB (for completion handling)
     ImGuiInputTextFlags_CallbackHistory     = 1 << 7,   // Call user function on pressing Up/Down arrows (for history handling)
     ImGuiInputTextFlags_CallbackAlways      = 1 << 8,   // Call user function every time. User code may query cursor position, modify text buffer.
-    ImGuiInputTextFlags_CallbackCharFilter  = 1 << 9,   // Call user function to filter character. Modify data->EventChar to replace/filter input, or return 1 to discard character.
+    ImGuiInputTextFlags_CallbackCharFilter  = 1 << 9,   // Call user function to filter character. Modify data->EventChar to replace/filter input, or return 1 in callback to discard character.
     ImGuiInputTextFlags_AllowTabInput       = 1 << 10,  // Pressing TAB input a '\t' character into the text field
     ImGuiInputTextFlags_CtrlEnterForNewLine = 1 << 11,  // In multi-line mode, unfocus with Enter, add new line with Ctrl+Enter (default is opposite: unfocus with Ctrl+Enter, add line with Enter).
     ImGuiInputTextFlags_NoHorizontalScroll  = 1 << 12,  // Disable following the cursor horizontally
@@ -652,6 +652,7 @@ enum ImGuiInputTextFlags_
     ImGuiInputTextFlags_Password            = 1 << 15,  // Password mode, display all characters as '*'
     ImGuiInputTextFlags_NoUndoRedo          = 1 << 16,  // Disable undo/redo. Note that input text owns the text data while active, if you want to provide your own undo/redo stack you need e.g. to call ClearActiveID().
     ImGuiInputTextFlags_CharsScientific     = 1 << 17,  // Allow 0123456789.+-*/eE (Scientific notation input)
+    ImGuiInputTextFlags_CallbackResize      = 1 << 18,  // Allow buffer capacity resize + notify when the string wants to be resized (for string types which hold a cache of their Size)
     // [Internal]
     ImGuiInputTextFlags_Multiline           = 1 << 20   // For internal use by InputTextMultiline()
 };
@@ -1415,27 +1416,30 @@ struct ImGuiStorage
 };
 
 // Shared state of InputText(), passed to callback when a ImGuiInputTextFlags_Callback* flag is used and the corresponding callback is triggered.
+// The callback function should return 0 by default.
+// Special processing:
+// - ImGuiInputTextFlags_CallbackCharFilter:  return 1 if the character is not allowed. You may also set 'EventChar=0' as any character replacement are allowed.
+// - ImGuiInputTextFlags_CallbackResize:      BufTextLen is set to the new desired string length so you can allocate or update known size. No need to initialize new characters or zero-terminator as InputText will do it.
 struct ImGuiTextEditCallbackData
 {
-    ImGuiInputTextFlags EventFlag;      // One of ImGuiInputTextFlags_Callback* // Read-only
+    ImGuiInputTextFlags EventFlag;      // One ImGuiInputTextFlags_Callback*    // Read-only
     ImGuiInputTextFlags Flags;          // What user passed to InputText()      // Read-only
     void*               UserData;       // What user passed to InputText()      // Read-only
 
-    // CharFilter event:
-    ImWchar             EventChar;      // Character input                      // Read-write (replace character or set to zero)
-
-    // Completion,History,Always events:
-    // If you modify the buffer contents make sure you update 'BufTextLen' and set 'BufDirty' to true.
-    ImGuiKey            EventKey;       // Key pressed (Up/Down/TAB)            // Read-only
-    char*               Buf;            // Current text buffer                  // Read-write (pointed data only, can't replace the actual pointer)
-    int                 BufTextLen;     // Current text length in bytes         // Read-write
-    int                 BufSize;        // Capacity (maximum text length + 1)   // Read-only
-    bool                BufDirty;       // Set if you modify Buf/BufTextLen!!   // Write
-    int                 CursorPos;      //                                      // Read-write
-    int                 SelectionStart; //                                      // Read-write (== to SelectionEnd when no selection)
-    int                 SelectionEnd;   //                                      // Read-write
+    // Arguments for the different callback events
+    // (If you modify the 'buf' contents make sure you update 'BufTextLen' and set 'BufDirty' to true!)
+    ImWchar             EventChar;      // Character input                      // Read-write   // [CharFilter] Replace character or set to zero. return 1 is equivalent to setting EventChar=0;
+    ImGuiKey            EventKey;       // Key pressed (Up/Down/TAB)            // Read-only    // [Completion,History]
+    char*               Buf;            // Current text buffer                  // Read-write   // [Resize] Can replace pointer / [Completion,History,Always] Only write to pointed data, don't replace the actual pointer!
+    int                 BufTextLen;     // Current text length in bytes         // Read-write   // [Resize,Completion,History,Always]
+    int                 BufSize;        // Capacity + 1 (max text length + 1)   // Read-only    // [Resize,Completion,History,Always]
+    bool                BufDirty;       // Set if you modify Buf/BufTextLen!!   // Write        // [Completion,History,Always]
+    int                 CursorPos;      //                                      // Read-write   // [Completion,History,Always]
+    int                 SelectionStart; //                                      // Read-write   // [Completion,History,Always] == to SelectionEnd when no selection)
+    int                 SelectionEnd;   //                                      // Read-write   // [Completion,History,Always]
 
     // NB: Helper functions for text manipulation. Calling those function loses selection.
+    ImGuiTextEditCallbackData();
     IMGUI_API void      DeleteChars(int pos, int bytes_count);
     IMGUI_API void      InsertChars(int pos, const char* text, const char* text_end = NULL);
     bool                HasSelection() const { return SelectionStart != SelectionEnd; }