Combo: amends for ImGuiComboFlags_WidthFitPreview. (#6881)

Amend 112d8fc

docs/CHANGELOG.txt

@@ -118,6 +118,7 @@ Other changes:
   be accepted by the widget when navigation highlight is visible. (#6802, #3092, #5759, #787)
 - BeginGroup(): Fixed a bug pushing line lower extent too far down when called after a call
   to SameLine() followed by manual cursor manipulation.
+- BeginCombo(): Added ImGuiComboFlags_WidthFitPreview flag. (#6881) [@mpv-enjoyer]
 - BeginListBox(): Fixed not consuming SetNextWindowXXX data when returning false.
 - Menus: Fixed a bug where activating an item in a child-menu and dragging mouse over the
   parent-menu would erroneously close the child-menu. (Regression from 1.88). (#6869)

imgui.h

@@ -1115,7 +1115,7 @@ enum ImGuiComboFlags_
     ImGuiComboFlags_HeightLargest           = 1 << 4,   // As many fitting items as possible
     ImGuiComboFlags_NoArrowButton           = 1 << 5,   // Display on the preview box without the square arrow button
     ImGuiComboFlags_NoPreview               = 1 << 6,   // Display only a square arrow button
-    ImGuiComboFlags_WidthFitPreview         = 1 << 7,   // Dynamic width depending on current selected element
+    ImGuiComboFlags_WidthFitPreview         = 1 << 7,   // Width dynamically calculated from preview contents
     ImGuiComboFlags_HeightMask_             = ImGuiComboFlags_HeightSmall | ImGuiComboFlags_HeightRegular | ImGuiComboFlags_HeightLarge | ImGuiComboFlags_HeightLargest,
 };
 

imgui_demo.cpp

@@ -1190,11 +1190,12 @@ static void ShowDemoWindowWidgets()
         static ImGuiComboFlags flags = 0;
         ImGui::CheckboxFlags("ImGuiComboFlags_PopupAlignLeft", &flags, ImGuiComboFlags_PopupAlignLeft);
         ImGui::SameLine(); HelpMarker("Only makes a difference if the popup is larger than the combo");
-        ImGui::CheckboxFlags("ImGuiComboFlags_WidthFitPreview", &flags, ImGuiComboFlags_WidthFitPreview);
         if (ImGui::CheckboxFlags("ImGuiComboFlags_NoArrowButton", &flags, ImGuiComboFlags_NoArrowButton))
             flags &= ~ImGuiComboFlags_NoPreview;     // Clear the other flag, as we cannot combine both
         if (ImGui::CheckboxFlags("ImGuiComboFlags_NoPreview", &flags, ImGuiComboFlags_NoPreview))
-            flags &= ~ImGuiComboFlags_NoArrowButton; // Clear the other flag, as we cannot combine both
+            flags &= ~(ImGuiComboFlags_NoArrowButton | ImGuiComboFlags_WidthFitPreview); // Clear the other flag, as we cannot combine both
+        if (ImGui::CheckboxFlags("ImGuiComboFlags_WidthFitPreview", &flags, ImGuiComboFlags_WidthFitPreview))
+            flags &= ~ImGuiComboFlags_NoPreview;
 
         // Using the generic BeginCombo() API, you have full control over how to display the combo contents.
         // (your selection data could be an index, a pointer to the object, an id for the object, a flag intrusively

imgui_widgets.cpp

@@ -1683,11 +1683,13 @@ bool ImGui::BeginCombo(const char* label, const char* preview_value, ImGuiComboF
     const ImGuiStyle& style = g.Style;
     const ImGuiID id = window->GetID(label);
     IM_ASSERT((flags & (ImGuiComboFlags_NoArrowButton | ImGuiComboFlags_NoPreview)) != (ImGuiComboFlags_NoArrowButton | ImGuiComboFlags_NoPreview)); // Can't use both flags together
+    if (flags & ImGuiComboFlags_WidthFitPreview)
+        IM_ASSERT((flags & (ImGuiComboFlags_NoPreview | ImGuiComboFlags_CustomPreview)) == 0);
 
     const float arrow_size = (flags & ImGuiComboFlags_NoArrowButton) ? 0.0f : GetFrameHeight();
     const ImVec2 label_size = CalcTextSize(label, NULL, true);
-    const float preview_width = (preview_value != nullptr) ? CalcTextSize(preview_value, NULL, true).x : 0.0f;
-    const float w = (flags & ImGuiComboFlags_NoPreview) ? arrow_size : ((flags & ImGuiComboFlags_WidthFitPreview) ? arrow_size + preview_width + style.ItemInnerSpacing.x * 2.0f : CalcItemWidth());
+    const float preview_width = ((flags & ImGuiComboFlags_WidthFitPreview) && (preview_value != NULL)) ? CalcTextSize(preview_value, NULL, true).x : 0.0f;
+    const float w = (flags & ImGuiComboFlags_NoPreview) ? arrow_size : ((flags & ImGuiComboFlags_WidthFitPreview) ? (arrow_size + preview_width + style.FramePadding.x * 2.0f) : CalcItemWidth());
     const ImRect bb(window->DC.CursorPos, window->DC.CursorPos + ImVec2(w, label_size.y + style.FramePadding.y * 2.0f));
     const ImRect total_bb(bb.Min, bb.Max + ImVec2(label_size.x > 0.0f ? style.ItemInnerSpacing.x + label_size.x : 0.0f, 0.0f));
     ItemSize(total_bb, style.FramePadding.y);