InputText: Word-Wrap: attempt to track cursor while resizing frame/parent. (#3237, #952, #1062, #7363)

imgui_internal.h

@@ -1247,6 +1247,7 @@ struct IMGUI_API ImGuiInputTextState
     float                   WrapWidth;              // word-wrapping width
     float                   CursorAnim;             // timer for cursor blink, reset on every user action so the cursor reappears immediately
     bool                    CursorFollow;           // set when we want scrolling to follow the current cursor position (not always!)
+    bool                    CursorCenterY;          // set when we want scrolling to be centered over the cursor position (while resizing a word-wrapping field)
     bool                    SelectedAllMouseLock;   // after a double-click to select all, we ignore further mouse drags to update selection
     bool                    Edited;                 // edited this frame
     bool                    WantReloadUserBuf;      // force a reload of user buf so it may be modified externally. may be automatic in future version.

imgui_widgets.cpp

@@ -4821,6 +4821,15 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
     if (is_password && !is_displaying_hint)
         PushPasswordFont();
 
+    // Word-wrapping: attempt to keep cursor in view while resizing frame/parent
+    // FIXME-WORDWRAP: It would be better to preserve same relative offset.
+    if (is_wordwrap && state != NULL && state->ID == id && state->WrapWidth != wrap_width)
+    {
+        state->CursorCenterY = true;
+        state->WrapWidth = wrap_width;
+        render_cursor = true;
+    }
+
     // Process mouse inputs and character inputs
     if (g.ActiveId == id)
     {
@@ -5414,6 +5423,7 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
         }
 
         // Scroll
+        float new_scroll_y = scroll_y;
         if (render_cursor && state->CursorFollow)
         {
             // Horizontal scroll in chunks of quarter width
@@ -5436,17 +5446,26 @@ bool ImGui::InputTextEx(const char* label, const char* hint, char* buf, int buf_
             {
                 // Test if cursor is vertically visible
                 if (cursor_offset.y - g.FontSize < scroll_y)
-                    scroll_y = ImMax(0.0f, cursor_offset.y - g.FontSize);
+                    new_scroll_y  = ImMax(0.0f, cursor_offset.y - g.FontSize);
                 else if (cursor_offset.y - (inner_size.y - style.FramePadding.y * 2.0f) >= scroll_y)
-                    scroll_y = cursor_offset.y - inner_size.y + style.FramePadding.y * 2.0f;
-                const float scroll_max_y = ImMax((text_size.y + style.FramePadding.y * 2.0f) - inner_size.y, 0.0f);
-                scroll_y = ImClamp(scroll_y, 0.0f, scroll_max_y);
-                draw_pos.y += (draw_window->Scroll.y - scroll_y);   // Manipulate cursor pos immediately avoid a frame of lag
-                draw_window->Scroll.y = scroll_y;
+                    new_scroll_y = cursor_offset.y - inner_size.y + style.FramePadding.y * 2.0f;
             }
-
             state->CursorFollow = false;
         }
+        if (state->CursorCenterY)
+        {
+            if (is_multiline)
+                new_scroll_y = cursor_offset.y - g.FontSize - (inner_size.y * 0.5f - style.FramePadding.y);
+            state->CursorCenterY = false;
+            render_cursor = false;
+        }
+        if (new_scroll_y != scroll_y)
+        {
+            const float scroll_max_y = ImMax((text_size.y + style.FramePadding.y * 2.0f) - inner_size.y, 0.0f);
+            scroll_y = ImClamp(new_scroll_y, 0.0f, scroll_max_y);
+            draw_pos.y += (draw_window->Scroll.y - scroll_y);   // Manipulate cursor pos immediately avoid a frame of lag
+            draw_window->Scroll.y = scroll_y;
+        }
 
         // Draw selection
         const ImVec2 draw_scroll = ImVec2(state->Scroll.x, 0.0f);