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

CHANGELOG.txt

@@ -52,6 +52,8 @@ Other Changes:
  - Window: Allow menu and popups windows from ignoring the style.WindowMinSize values so short menus/popups are not padded. (#1909)
  - Window: Added global io.OptResizeWindowsFromEdges option to enable resizing windows from their edges and from the lower-left corner. (#1495)
  - Window: Collapse button shows hovering highlight + clicking and dragging on it allows to drag the window as well. 
+ - InputText: Added support for buffer size/capacity changes via the ImGuiInputTextFlags_CallbackResize flag. (#2006, #1443, #1008).
+ - InputText: Fixed minor off-by-one issue when submitting a buffer size smaller than the initial zero-terminated buffer contents.
  - Drag and Drop: Fixed an incorrect assert when dropping a source that is submitted after the target (bug introduced with 1.62 changes 
    related to the addition of IsItemDeactivated()). (#1875, #143)
  - Drag and Drop: Fixed ImGuiDragDropFlags_SourceNoDisableHover to affect hovering state prior to calling IsItemHovered() + fixed description. (#143)
@@ -60,7 +62,6 @@ Other Changes:
  - Drag and Drop: Payload stays available and under the mouse if the source stops being submitted, however the tooltip is replaced by "...". (#1725)
  - Drag and Drop: Added ImGuiDragDropFlags_SourceAutoExpirePayload flag to force payload to expire if the source stops being submitted. (#1725, #143).
  - IsItemHovered(): Added ImGuiHoveredFlags_AllowWhenDisabled flag to query hovered status on disabled items. (#1940, #211)
- - InputText: Fixed minor off-by-one issue when submitting a buffer size smaller than the initial zero-terminated buffer contents.
  - Selectable: Added ImGuiSelectableFlags_Disabled flag in the public API. (#211)
  - Misc: Added IMGUI_VERSION_NUM for easy compile-time testing. (#2025)
  - Misc: Added ImGuiMouseCursor_Hand cursor enum + corresponding software cursor. (#1913, 1914) [@aiekick, @ocornut] 

TODO.txt

@@ -66,7 +66,6 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - input text: expose CursorPos in char filter event (#816)
  - input text: access public fields via a non-callback API e.g. InputTextGetState("xxx") that may return NULL if not active.
  - input text: flag to disable live update of the user buffer (also applies to float/int text input) (#701)
- - input text: way to dynamically grow the buffer without forcing the user to initially allocate for worse case, e.g. more natural std::string (follow up on #200)
  - input text: hover tooltip could show unclamped text
  - input text: option to Tab after an Enter validation.
  - input text: add ImGuiInputTextFlags_EnterToApply? (off #218)

imgui.cpp

@@ -10535,15 +10535,23 @@ static void STB_TEXTEDIT_DELETECHARS(STB_TEXTEDIT_STRING* obj, int pos, int n)
 
 static bool STB_TEXTEDIT_INSERTCHARS(STB_TEXTEDIT_STRING* obj, int pos, const ImWchar* new_text, int new_text_len)
 {
+    const bool is_resizable = (obj->UserFlags & ImGuiInputTextFlags_CallbackResize) != 0;
     const int text_len = obj->CurLenW;
     IM_ASSERT(pos <= text_len);
-    if (new_text_len + text_len + 1 > obj->Text.Size)
-        return false;
 
     const int new_text_len_utf8 = ImTextCountUtf8BytesFromStr(new_text, new_text + new_text_len);
-    if (new_text_len_utf8 + obj->CurLenA + 1 > obj->BufCapacityA)
+    if (!is_resizable && (new_text_len_utf8 + obj->CurLenA + 1 > obj->BufCapacityA))
         return false;
 
+    // Grow internal buffer if needed
+    if (new_text_len + text_len + 1 > obj->Text.Size)
+    {
+        if (!is_resizable)
+            return false;
+        IM_ASSERT(text_len < obj->Text.Size);
+        obj->Text.resize(text_len + ImClamp(new_text_len * 4, 32, ImMax(256, new_text_len)) + 1);
+    }
+
     ImWchar* text = obj->Text.Data;
     if (pos != text_len)
         memmove(text + pos + new_text_len, text + pos, (size_t)(text_len - pos) * sizeof(ImWchar));
@@ -10585,6 +10593,11 @@ void ImGuiTextEditState::OnKeyPressed(int key)
     CursorAnimReset();
 }
 
+ImGuiTextEditCallbackData::ImGuiTextEditCallbackData()
+{
+    memset(this, 0, sizeof(*this));
+}
+
 // Public API to manipulate UTF-8 text
 // We expose UTF-8 to the user (unlike the STB_TEXTEDIT_* functions which are manipulating wchar)
 // FIXME: The existence of this rarely exercised code path is a bit of a nuisance.
@@ -10693,6 +10706,8 @@ bool ImGui::InputTextEx(const char* label, char* buf, int buf_size, const ImVec2
 
     IM_ASSERT(!((flags & ImGuiInputTextFlags_CallbackHistory) && (flags & ImGuiInputTextFlags_Multiline))); // Can't use both together (they both use up/down keys)
     IM_ASSERT(!((flags & ImGuiInputTextFlags_CallbackCompletion) && (flags & ImGuiInputTextFlags_AllowTabInput))); // Can't use both together (they both use tab key)
+    if (flags & ImGuiInputTextFlags_CallbackResize)
+        IM_ASSERT(callback != NULL);
 
     ImGuiContext& g = *GImGui;
     const ImGuiIO& io = g.IO;
@@ -10818,6 +10833,7 @@ bool ImGui::InputTextEx(const char* label, char* buf, int buf_size, const ImVec2
 
     bool value_changed = false;
     bool enter_pressed = false;
+    int backup_current_text_length = 0;
 
     if (g.ActiveId == id)
     {
@@ -10831,7 +10847,11 @@ bool ImGui::InputTextEx(const char* label, char* buf, int buf_size, const ImVec2
             edit_state.CursorClamp();
         }
 
+        backup_current_text_length = edit_state.CurLenA;
         edit_state.BufCapacityA = buf_size;
+        edit_state.UserFlags = flags;
+        edit_state.UserCallback = callback;
+        edit_state.UserCallbackData = callback_user_data;
 
         // Although we are active we don't prevent mouse from hovering other elements unless we are interacting right now with the widget.
         // Down the line we should have a cleaner library-wide concept of Selected vs Active.
@@ -11009,13 +11029,15 @@ bool ImGui::InputTextEx(const char* label, char* buf, int buf_size, const ImVec2
 
     if (g.ActiveId == id)
     {
+        const char* apply_new_text = NULL;
+        int apply_new_text_length = 0;
         if (cancel_edit)
         {
             // Restore initial value. Only return true if restoring to the initial value changes the current buffer contents.
             if (is_editable && strncmp(buf, edit_state.InitialText.Data, buf_size) != 0)
             {
-                ImStrncpy(buf, edit_state.InitialText.Data, buf_size);
-                value_changed = true;
+                apply_new_text = edit_state.InitialText.Data;
+                apply_new_text_length = buf_size - 1;
             }
         }
 
@@ -11100,13 +11122,40 @@ bool ImGui::InputTextEx(const char* label, char* buf, int buf_size, const ImVec2
                 }
             }
 
-            // Copy back to user buffer
+            // Will copy result string if modified
             if (is_editable && strcmp(edit_state.TempTextBuffer.Data, buf) != 0)
             {
-                ImStrncpy(buf, edit_state.TempTextBuffer.Data, edit_state.CurLenA + 1);
-                value_changed = true;
+                apply_new_text = edit_state.TempTextBuffer.Data;
+                apply_new_text_length = edit_state.CurLenA;
+            }
+        }
+
+        // Copy result to user buffer
+        if (apply_new_text)
+        {
+            IM_ASSERT(apply_new_text_length >= 0);
+            if (backup_current_text_length != apply_new_text_length && (flags & ImGuiInputTextFlags_CallbackResize))
+            {
+                ImGuiTextEditCallbackData callback_data;
+                callback_data.EventFlag = ImGuiInputTextFlags_CallbackResize;
+                callback_data.Flags = flags;
+                callback_data.Buf = buf;
+                callback_data.BufTextLen = edit_state.CurLenA;
+                callback_data.BufSize = ImMax(buf_size, apply_new_text_length + 1);
+                callback_data.UserData = callback_user_data;
+                callback(&callback_data);
+                buf = callback_data.Buf;
+                buf_size = callback_data.BufSize;
             }
+            IM_ASSERT(apply_new_text_length <= buf_size);
+            ImStrncpy(buf, edit_state.TempTextBuffer.Data, apply_new_text_length + 1);
+            value_changed = true;
         }
+
+        // Clear temporary user storage
+        edit_state.UserFlags = 0;
+        edit_state.UserCallback = NULL;
+        edit_state.UserCallbackData = NULL;
     }
 
     // Release active ID at the end of the function (so e.g. pressing Return still does a final application of the value)

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; }

imgui_internal.h

@@ -443,6 +443,11 @@ struct IMGUI_API ImGuiTextEditState
     bool                    CursorFollow;
     bool                    SelectedAllMouseLock;
 
+    // Temporarily set when active
+    ImGuiInputTextFlags     UserFlags;
+    ImGuiTextEditCallback   UserCallback;
+    void*                   UserCallbackData;
+
     ImGuiTextEditState()                            { memset(this, 0, sizeof(*this)); }
     void                CursorAnimReset()           { CursorAnim = -0.30f; }                                   // After a user-input the cursor stays on for a while without blinking
     void                CursorClamp()               { StbState.cursor = ImMin(StbState.cursor, CurLenW); StbState.select_start = ImMin(StbState.select_start, CurLenW); StbState.select_end = ImMin(StbState.select_end, CurLenW); }