InputText: callback InsertChars() support resize callbacks correctly …

…(followup to 24ff259) + fixed demo to use those functions.  (#2006, #1443, #1008).

CHANGELOG.txt

@@ -86,6 +86,8 @@ Other Changes:
  - Metrics: Added io.MetricsRenderWindow to reflect the number of visible windows.
  - Metrics: Added io.MetricsActiveAllocations, moving away from the cross-context global counters than we previously used. (#1565, #1599, #586)
  - Demo: Added basic Drag and Drop demo. (#143)
+ - Demo: Modified the Console example to use InsertChars() in the input text callback instead of poking directly into the buffer.
+   Although this won't make a difference in the example itself, using InsertChars() will honor the resizing callback properly. (#2006, #1443, #1008).
  - Demo: Clarified the use of IsItemHovered()/IsItemActive() right after being in the "Active, Focused, Hovered & Focused Tests" section.
  - Examples: Tweaked the main.cpp of each example.
  - Examples: Metal: Added Metal rendering backend. (#1929, #1873) [@warrenm]

imgui.cpp

@@ -10622,9 +10622,23 @@ void ImGuiInputTextCallbackData::DeleteChars(int pos, int bytes_count)
 
 void ImGuiInputTextCallbackData::InsertChars(int pos, const char* new_text, const char* new_text_end)
 {
+    const bool is_resizable = (Flags & ImGuiInputTextFlags_CallbackResize) != 0;
     const int new_text_len = new_text_end ? (int)(new_text_end - new_text) : (int)strlen(new_text);
-    if (new_text_len + BufTextLen + 1 >= BufSize)
-        return;
+    if (new_text_len + BufTextLen >= BufSize)
+    {
+        if (!is_resizable)
+            return;
+
+        // Contrary to STB_TEXTEDIT_INSERTCHARS() this is working in the UTF8 buffer, hence the midly similar code (until we remove the U16 buffer alltogether!)
+        ImGuiContext& g = *GImGui;
+        ImGuiInputTextState* edit_state = &g.InputTextState;
+        IM_ASSERT(edit_state->ID != 0 && g.ActiveId == edit_state->ID);
+        IM_ASSERT(Buf == edit_state->TempBuffer.Data);
+        int new_buf_size = BufTextLen + ImClamp(new_text_len * 4, 32, ImMax(256, new_text_len)) + 1;
+        edit_state->TempBuffer.reserve(new_buf_size + 1);
+        Buf = edit_state->TempBuffer.Data;
+        BufSize = edit_state->BufCapacityA = new_buf_size;
+    }
 
     if (BufTextLen != pos)
         memmove(Buf + pos + new_text_len, Buf + pos, (size_t)(BufTextLen - pos));
@@ -10710,8 +10724,6 @@ 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;
@@ -10721,6 +10733,9 @@ bool ImGui::InputTextEx(const char* label, char* buf, int buf_size, const ImVec2
     const bool is_editable = (flags & ImGuiInputTextFlags_ReadOnly) == 0;
     const bool is_password = (flags & ImGuiInputTextFlags_Password) != 0;
     const bool is_undoable = (flags & ImGuiInputTextFlags_NoUndoRedo) == 0;
+    const bool is_resizable = (flags & ImGuiInputTextFlags_CallbackResize) != 0;
+    if (is_resizable)
+        IM_ASSERT(callback != NULL); // Must provide a callback if you set the ImGuiInputTextFlags_CallbackResize flag!
 
     if (is_multiline) // Open group before calling GetID() because groups tracks id created within their scope, 
         BeginGroup();
@@ -11056,7 +11071,7 @@ bool ImGui::InputTextEx(const char* label, char* buf, int buf_size, const ImVec2
             // FIXME-OPT: CPU waste to do this every time the widget is active, should mark dirty state from the stb_textedit callbacks.
             if (is_editable)
             {
-                edit_state.TempBuffer.resize(edit_state.TextW.Size * 4);
+                edit_state.TempBuffer.resize(edit_state.TextW.Size * 4 + 1);
                 ImTextStrToUtf8(edit_state.TempBuffer.Data, edit_state.TempBuffer.Size, edit_state.TextW.Data, NULL);
             }
 
@@ -11119,6 +11134,8 @@ bool ImGui::InputTextEx(const char* label, char* buf, int buf_size, const ImVec2
                     if (callback_data.BufDirty)
                     {
                         IM_ASSERT(callback_data.BufTextLen == (int)strlen(callback_data.Buf)); // You need to maintain BufTextLen if you change the text!
+                        if (callback_data.BufTextLen > backup_current_text_length && is_resizable)
+                            edit_state.TextW.resize(edit_state.TextW.Size + (callback_data.BufTextLen - backup_current_text_length));
                         edit_state.CurLenW = ImTextStrFromUtf8(edit_state.TextW.Data, edit_state.TextW.Size, callback_data.Buf, NULL);
                         edit_state.CurLenA = callback_data.BufTextLen;  // Assume correct length and valid UTF-8 from user, saves us an extra strlen()
                         edit_state.CursorAnimReset();
@@ -11138,7 +11155,7 @@ bool ImGui::InputTextEx(const char* label, char* buf, int buf_size, const ImVec2
         if (apply_new_text)
         {
             IM_ASSERT(apply_new_text_length >= 0);
-            if (backup_current_text_length != apply_new_text_length && (flags & ImGuiInputTextFlags_CallbackResize))
+            if (backup_current_text_length != apply_new_text_length && is_resizable)
             {
                 ImGuiInputTextCallbackData callback_data;
                 callback_data.EventFlag = ImGuiInputTextFlags_CallbackResize;

imgui.h

@@ -1419,15 +1419,16 @@ struct ImGuiStorage
 // 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 the size on your side of the fence. No need to initialize new characters or zero-terminator as InputText will do it.
+// - ImGuiInputTextFlags_CallbackResize:      notified by InputText() when the string is resized. BufTextLen is set to the new desired string length so you can update the string size on your side of the fence. You can also replace Buf pointer if your underlying data is reallocated. No need to initialize new characters or zero-terminator as InputText will do it right after the resize callback.
 struct ImGuiInputTextCallbackData
 {
     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
 
     // Arguments for the different callback events
-    // (If you modify the 'buf' contents make sure you update 'BufTextLen' and set 'BufDirty' to true!)
+    // - To modify the text buffer in a callback, prefer using the InsertChars() / DeleteChars() function. InsertChars() will take care of calling the resize callback if necessary.
+    // - If you know your edits are not going to resize the underlying buffer allocation, you may modify the contents of 'Buf[]' directly. You need to update 'BufTextLen' accordingly (0 <= BufTextLen < BufSize) and set 'BufDirty'' to true so InputText can update its internal state.
     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;            // Text buffer                          // Read-write   // [Resize] Can replace pointer / [Completion,History,Always] Only write to pointed data, don't replace the actual pointer!
@@ -1438,7 +1439,8 @@ struct ImGuiInputTextCallbackData
     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.
+    // Helper functions for text manipulation.
+    // Use those function to benefit from the CallbackResize behaviors. Calling those function reset the selection.
     ImGuiInputTextCallbackData();
     IMGUI_API void      DeleteChars(int pos, int bytes_count);
     IMGUI_API void      InsertChars(int pos, const char* text, const char* text_end = NULL);

imgui_demo.cpp

@@ -36,7 +36,6 @@
 
 #ifdef _MSC_VER
 #pragma warning (disable: 4996) // 'This function or variable may be unsafe': strcpy, strdup, sprintf, vsnprintf, sscanf, fopen
-#define snprintf  _snprintf
 #define vsnprintf _vsnprintf
 #endif
 #ifdef __clang__
@@ -2809,14 +2808,15 @@ struct ExampleAppConsole
         bool reclaim_focus = false;
         if (ImGui::InputText("Input", InputBuf, IM_ARRAYSIZE(InputBuf), ImGuiInputTextFlags_EnterReturnsTrue|ImGuiInputTextFlags_CallbackCompletion|ImGuiInputTextFlags_CallbackHistory, &TextEditCallbackStub, (void*)this))
         {
-            Strtrim(InputBuf);
-            if (InputBuf[0])
-                ExecCommand(InputBuf);
-            strcpy(InputBuf, "");
+            char* s = InputBuf;
+            Strtrim(s);
+            if (s[0])
+                ExecCommand(s);
+            strcpy(s, "");
             reclaim_focus = true;
         }
 
-        // Demonstrate keeping focus on the input box
+        // Auto-focus on window apparition
         ImGui::SetItemDefaultFocus();
         if (reclaim_focus)
             ImGui::SetKeyboardFocusHere(-1); // Auto focus previous widget
@@ -2959,9 +2959,9 @@ struct ExampleAppConsole
                 // A better implementation would preserve the data on the current input line along with cursor position.
                 if (prev_history_pos != HistoryPos)
                 {
-                    int sz = (int)snprintf(data->Buf, (size_t)data->BufSize, "%s", (HistoryPos >= 0) ? History[HistoryPos] : "");
-                    data->CursorPos = data->SelectionStart = data->SelectionEnd = data->BufTextLen = sz;
-                    data->BufDirty = true;
+                    const char* history_str = (HistoryPos >= 0) ? History[HistoryPos] : "";
+                    data->DeleteChars(0, data->BufTextLen);
+                    data->InsertChars(0, history_str);
                 }
             }
         }