Internals: Reworked RenderTextEllipsis() to satisfy what we need for table headers.

imgui.cpp

@@ -2424,7 +2424,7 @@ void ImGui::RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, cons
 
 
 // Another overly complex function until we reorganize everything into a nice all-in-one helper.
-// This is made more complex because we have dissociated the layout rectangle (pos_min..pos_max) which define where the ellipsis is, from actual clipping and limit of the ellipsis display.
+// This is made more complex because we have dissociated the layout rectangle (pos_min..pos_max) which define _where_ the ellipsis is, from actual clipping of text and limit of the ellipsis display.
 // This is because in the context of tabs we selectively hide part of the text when the Close Button appears, but we don't want the ellipsis to move. 
 void    ImGui::RenderTextEllipsis(ImDrawList* draw_list, const ImVec2& pos_min, const ImVec2& pos_max, float clip_max_x, float ellipsis_max_x, const char* text, const char* text_end_full, const ImVec2* text_size_if_known)
 {
@@ -2435,27 +2435,36 @@ void    ImGui::RenderTextEllipsis(ImDrawList* draw_list, const ImVec2& pos_min,
 
     if (text_size.x > pos_max.x - pos_min.x)
     {
+        // Hello wo...
+        // |       |   |
+        // min   max   ellipsis_max
+        //          <-> this is generally some padding value
 
+        // FIXME-STYLE: RenderPixelEllipsis() style should use actual font data.
         const ImFont* font = draw_list->_Data->Font;
         const float font_size = draw_list->_Data->FontSize;
         const int ellipsis_dot_count = 3;
         const float ellipsis_width = (1.0f + 1.0f) * ellipsis_dot_count - 1.0f;
         const char* text_end_ellipsis = NULL;
-        float text_size_clipped_x = font->CalcTextSizeA(font_size, (pos_max.x - pos_min.x) - ellipsis_width + 1.0f, 0.0f, text, text_end_full, &text_end_ellipsis).x;
+
-        if (text == text_end_ellipsis && text_end_ellipsis < text_end_full)    // Always display at least 1 character if there's no room for character + ellipsis
+        float text_width = ImMax((pos_max.x - ellipsis_width) - pos_min.x, 1.0f);
+        float text_size_clipped_x = font->CalcTextSizeA(font_size, text_width, 0.0f, text, text_end_full, &text_end_ellipsis).x;
+        if (text == text_end_ellipsis && text_end_ellipsis < text_end_full)
         {
+            // Always display at least 1 character if there's no room for character + ellipsis
             text_end_ellipsis = text + ImTextCountUtf8BytesFromChar(text, text_end_full);
             text_size_clipped_x = font->CalcTextSizeA(font_size, FLT_MAX, 0.0f, text, text_end_ellipsis).x;
         }
-        while (text_end_ellipsis > text && ImCharIsBlankA(text_end_ellipsis[-1])) // Trim trailing space
+        while (text_end_ellipsis > text && ImCharIsBlankA(text_end_ellipsis[-1]))
         {
+            // Trim trailing space before ellipsis
             text_end_ellipsis--;
             text_size_clipped_x -= font->CalcTextSizeA(font_size, FLT_MAX, 0.0f, text_end_ellipsis, text_end_ellipsis + 1).x; // Ascii blanks are always 1 byte
         }
         RenderTextClippedEx(draw_list, pos_min, ImVec2(clip_max_x, pos_max.y), text, text_end_ellipsis, &text_size, ImVec2(0.0f, 0.0f));
 
         const float ellipsis_x = pos_min.x + text_size_clipped_x + 1.0f;
-        if (ellipsis_x + ellipsis_width <= ellipsis_max_x)
+        if (ellipsis_x + ellipsis_width - 1.0f <= ellipsis_max_x)
             RenderPixelEllipsis(draw_list, ImVec2(ellipsis_x, pos_min.y), GetColorU32(ImGuiCol_Text), ellipsis_dot_count);
     }
     else

imgui_widgets.cpp

@@ -7077,7 +7077,7 @@ bool ImGui::TabItemLabelAndCloseButton(ImDrawList* draw_list, const ImRect& bb,
         text_pixel_clip_bb.Max.x -= close_button_sz;
     }
 
-    float ellipsis_max_x = close_button_visible ? -FLT_MAX : bb.Max.x;
+    float ellipsis_max_x = close_button_visible ? text_pixel_clip_bb.Max.x : bb.Max.x - 1.0f;
     RenderTextEllipsis(draw_list, text_ellipsis_clip_bb.Min, text_ellipsis_clip_bb.Max, text_pixel_clip_bb.Max.x, ellipsis_max_x, label, NULL, &label_size);
 
     return close_button_pressed;