Tabs, Style: reworked selected overline rendering to better accommodate for rounded tabs. (#8334)

docs/CHANGELOG.txt

@@ -54,6 +54,10 @@ Other changes:
 - Windows: legacy SetWindowFontScale() is properly inherited by nested child
   windows. Note that an upcoming major release should make this obsolete,
   but in the meanwhile it works better now. (#2701, #8138, #1018)
+- Tabs, Style: reworked selected overline rendering to better accommodate
+  for rounded tabs. Reduced default thickness (style.TabBarOverlineSize),
+  increased default rounding (style.TabRounding). (#8334) [@Kian738, @ocornut]
+  styles as the current look is not right (but ImGuiCol_TabSelectedOverline stays the same).
 - Examples: DirectX12: Reduced number of frame in flight from 3 to 2 in
   provided example, to reduce latency.
 - Examples: Vulkan: better handle VK_SUBOPTIMAL_KHR being returned by

imgui.cpp

@@ -1334,11 +1334,11 @@ ImGuiStyle::ImGuiStyle()
     GrabMinSize                 = 12.0f;            // Minimum width/height of a grab box for slider/scrollbar
     GrabRounding                = 0.0f;             // Radius of grabs corners rounding. Set to 0.0f to have rectangular slider grabs.
     LogSliderDeadzone           = 4.0f;             // The size in pixels of the dead-zone around zero on logarithmic sliders that cross zero.
-    TabRounding                 = 4.0f;             // Radius of upper corners of a tab. Set to 0.0f to have rectangular tabs.
+    TabRounding                 = 5.0f;             // Radius of upper corners of a tab. Set to 0.0f to have rectangular tabs.
     TabBorderSize               = 0.0f;             // Thickness of border around tabs.
     TabMinWidthForCloseButton   = 0.0f;             // Minimum width for close button to appear on an unselected tab when hovered. Set to 0.0f to always show when hovering, set to FLT_MAX to never show close button unless selected.
     TabBarBorderSize            = 1.0f;             // Thickness of tab-bar separator, which takes on the tab active color to denote focus.
-    TabBarOverlineSize          = 2.0f;             // Thickness of tab-bar overline, which highlights the selected tab-bar.
+    TabBarOverlineSize          = 1.0f;             // Thickness of tab-bar overline, which highlights the selected tab-bar.
     TableAngledHeadersAngle     = 35.0f * (IM_PI / 180.0f); // Angle of angled headers (supported values range from -50 degrees to +50 degrees).
     TableAngledHeadersTextAlign = ImVec2(0.5f,0.0f);// Alignment of angled headers within the cell
     ColorButtonPosition         = ImGuiDir_Right;   // Side of the color button in the ColorEdit4 widget (left/right). Defaults to ImGuiDir_Right.

imgui_demo.cpp

@@ -7966,7 +7966,7 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
             ImGui::SliderFloat("FrameBorderSize", &style.FrameBorderSize, 0.0f, 1.0f, "%.0f");
             ImGui::SliderFloat("TabBorderSize", &style.TabBorderSize, 0.0f, 1.0f, "%.0f");
             ImGui::SliderFloat("TabBarBorderSize", &style.TabBarBorderSize, 0.0f, 2.0f, "%.0f");
-            ImGui::SliderFloat("TabBarOverlineSize", &style.TabBarOverlineSize, 0.0f, 2.0f, "%.0f");
+            ImGui::SliderFloat("TabBarOverlineSize", &style.TabBarOverlineSize, 0.0f, 3.0f, "%.0f");
             ImGui::SameLine(); HelpMarker("Overline is only drawn over the selected tab when ImGuiTabBarFlags_DrawSelectedOverline is set.");
 
             ImGui::SeparatorText("Rounding");

imgui_widgets.cpp

@@ -10150,11 +10150,21 @@ bool    ImGui::TabItemEx(ImGuiTabBar* tab_bar, const char* label, bool* p_open,
     TabItemBackground(display_draw_list, bb, flags, tab_col);
     if (tab_contents_visible && (tab_bar->Flags & ImGuiTabBarFlags_DrawSelectedOverline) && style.TabBarOverlineSize > 0.0f)
     {
-        float x_offset = IM_TRUNC(0.4f * style.TabRounding);
-        if (x_offset < 2.0f * g.CurrentDpiScale)
-            x_offset = 0.0f;
-        float y_offset = 1.0f * g.CurrentDpiScale;
-        display_draw_list->AddLine(bb.GetTL() + ImVec2(x_offset, y_offset), bb.GetTR() + ImVec2(-x_offset, y_offset), GetColorU32(tab_bar_focused ? ImGuiCol_TabSelectedOverline : ImGuiCol_TabDimmedSelectedOverline), style.TabBarOverlineSize);
+        // Might be moved to TabItemBackground() ?
+        ImVec2 tl = bb.GetTL() + ImVec2(0, 1.0f * g.CurrentDpiScale);
+        ImVec2 tr = bb.GetTR() + ImVec2(0, 1.0f * g.CurrentDpiScale);
+        ImU32 overline_col = GetColorU32(tab_bar_focused ? ImGuiCol_TabSelectedOverline : ImGuiCol_TabDimmedSelectedOverline);
+        if (style.TabRounding > 0.0f)
+        {
+            float rounding = style.TabRounding;
+            display_draw_list->PathArcToFast(tl + ImVec2(+rounding, +rounding), rounding, 7, 9);
+            display_draw_list->PathArcToFast(tr + ImVec2(-rounding, +rounding), rounding, 9, 11);
+            display_draw_list->PathStroke(overline_col, 0, style.TabBarOverlineSize);
+        }
+        else
+        {
+            display_draw_list->AddLine(tl - ImVec2(0.5f, 0.5f), tr - ImVec2(0.5f, 0.5f), overline_col, style.TabBarOverlineSize);
+        }
     }
     RenderNavCursor(bb, id);