TabBar, Style: added style.TabBarBorderSize and associated ImGuiStyleVar_TabBarBorderSize. (#6820, #4859, #5022, #5239)

Cherry-picked from docking's 64b1e44

docs/CHANGELOG.txt

@@ -122,6 +122,8 @@ Other changes:
 - Windows: Layout of Close/Collapse buttons uses style.ItemInnerSpacing.x between items,
   stopped incorrectly using FramePadding in a way where hit-boxes could overlap when
   setting large values. (#6749)
+- TabBar, Style: added style.TabBarBorderSize and associated ImGuiStyleVar_TabBarBorderSize.
+  Tweaked rendering of that separator to allow thicker values. (#6820, #4859, #5022, #5239)
 - InputFloat, SliderFloat, DragFloat: always turn both '.' and ',' into the current decimal
   point character when using Decimal/Scientific character filter. (#6719, #2278) [@adamsepp]
 - ColorEdit, ColorPicker: Manipulating options popup don't mark item as edited. (#6722)

imgui.cpp

@@ -1185,6 +1185,7 @@ ImGuiStyle::ImGuiStyle()
     TabRounding             = 4.0f;             // 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.
     ColorButtonPosition     = ImGuiDir_Right;   // Side of the color button in the ColorEdit4 widget (left/right). Defaults to ImGuiDir_Right.
     ButtonTextAlign         = ImVec2(0.5f,0.5f);// Alignment of button text when button is larger than text.
     SelectableTextAlign     = ImVec2(0.0f,0.0f);// Alignment of selectable text. Defaults to (0.0f, 0.0f) (top-left aligned). It's generally important to keep this left-aligned if you want to lay multiple items on a same line.
@@ -3140,6 +3141,7 @@ static const ImGuiDataVarInfo GStyleVarInfo[] =
     { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, GrabMinSize) },         // ImGuiStyleVar_GrabMinSize
     { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, GrabRounding) },        // ImGuiStyleVar_GrabRounding
     { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, TabRounding) },         // ImGuiStyleVar_TabRounding
+    { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, TabBarBorderSize) },    // ImGuiStyleVar_TabBarBorderSize
     { ImGuiDataType_Float, 2, (ImU32)IM_OFFSETOF(ImGuiStyle, ButtonTextAlign) },     // ImGuiStyleVar_ButtonTextAlign
     { ImGuiDataType_Float, 2, (ImU32)IM_OFFSETOF(ImGuiStyle, SelectableTextAlign) }, // ImGuiStyleVar_SelectableTextAlign
     { ImGuiDataType_Float, 1, (ImU32)IM_OFFSETOF(ImGuiStyle, SeparatorTextBorderSize) },// ImGuiStyleVar_SeparatorTextBorderSize

imgui.h

@@ -1645,6 +1645,7 @@ enum ImGuiStyleVar_
     ImGuiStyleVar_GrabMinSize,         // float     GrabMinSize
     ImGuiStyleVar_GrabRounding,        // float     GrabRounding
     ImGuiStyleVar_TabRounding,         // float     TabRounding
+    ImGuiStyleVar_TabBarBorderSize,    // float     TabBarBorderSize
     ImGuiStyleVar_ButtonTextAlign,     // ImVec2    ButtonTextAlign
     ImGuiStyleVar_SelectableTextAlign, // ImVec2    SelectableTextAlign
     ImGuiStyleVar_SeparatorTextBorderSize,// float  SeparatorTextBorderSize
@@ -1912,6 +1913,7 @@ struct ImGuiStyle
     float       TabRounding;                // Radius of upper corners of a tab. Set to 0.0f to have rectangular tabs.
     float       TabBorderSize;              // Thickness of border around tabs.
     float       TabMinWidthForCloseButton;  // 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.
+    float       TabBarBorderSize;           // Thickness of tab-bar separator, which takes on the tab active color to denote focus.
     ImGuiDir    ColorButtonPosition;        // Side of the color button in the ColorEdit4 widget (left/right). Defaults to ImGuiDir_Right.
     ImVec2      ButtonTextAlign;            // Alignment of button text when button is larger than text. Defaults to (0.5f, 0.5f) (centered).
     ImVec2      SelectableTextAlign;        // Alignment of selectable text. Defaults to (0.0f, 0.0f) (top-left aligned). It's generally important to keep this left-aligned if you want to lay multiple items on a same line.

imgui_demo.cpp

@@ -6369,6 +6369,7 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
             ImGui::SliderFloat("PopupBorderSize", &style.PopupBorderSize, 0.0f, 1.0f, "%.0f");
             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::SeparatorText("Rounding");
             ImGui::SliderFloat("WindowRounding", &style.WindowRounding, 0.0f, 12.0f, "%.0f");

imgui_internal.h

@@ -2551,6 +2551,8 @@ struct IMGUI_API ImGuiTabBar
     float               ScrollingSpeed;
     float               ScrollingRectMinX;
     float               ScrollingRectMaxX;
+    float               SeparatorMinX;
+    float               SeparatorMaxX;
     ImGuiID             ReorderRequestTabId;
     ImS16               ReorderRequestOffset;
     ImS8                BeginCount;

imgui_widgets.cpp

@@ -7788,6 +7788,8 @@ bool    ImGui::BeginTabBar(const char* str_id, ImGuiTabBarFlags flags)
     ImGuiTabBar* tab_bar = g.TabBars.GetOrAddByKey(id);
     ImRect tab_bar_bb = ImRect(window->DC.CursorPos.x, window->DC.CursorPos.y, window->WorkRect.Max.x, window->DC.CursorPos.y + g.FontSize + g.Style.FramePadding.y * 2);
     tab_bar->ID = id;
+    tab_bar->SeparatorMinX = tab_bar->BarRect.Min.x - IM_FLOOR(window->WindowPadding.x * 0.5f);
+    tab_bar->SeparatorMaxX = tab_bar->BarRect.Max.x + IM_FLOOR(window->WindowPadding.x * 0.5f);
     return BeginTabBarEx(tab_bar, tab_bar_bb, flags | ImGuiTabBarFlags_IsFocused);
 }
 
@@ -7798,6 +7800,7 @@ bool    ImGui::BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& tab_bar_bb, ImG
     if (window->SkipItems)
         return false;
 
+    IM_ASSERT(tab_bar->ID != 0);
     if ((flags & ImGuiTabBarFlags_DockNode) == 0)
         PushOverrideID(tab_bar->ID);
 
@@ -7840,12 +7843,12 @@ bool    ImGui::BeginTabBarEx(ImGuiTabBar* tab_bar, const ImRect& tab_bar_bb, ImG
     window->DC.CursorPos = ImVec2(tab_bar->BarRect.Min.x, tab_bar->BarRect.Max.y + tab_bar->ItemSpacingY);
 
     // Draw separator
+    // (it would be misleading to draw this in EndTabBar() suggesting that it may be drawn over tabs, as tab bar are appendable)
     const ImU32 col = GetColorU32((flags & ImGuiTabBarFlags_IsFocused) ? ImGuiCol_TabActive : ImGuiCol_TabUnfocusedActive);
-    const float y = tab_bar->BarRect.Max.y - 1.0f;
+    if (g.Style.TabBarBorderSize > 0.0f)
     {
-        const float separator_min_x = tab_bar->BarRect.Min.x - IM_FLOOR(window->WindowPadding.x * 0.5f);
-        const float separator_max_x = tab_bar->BarRect.Max.x + IM_FLOOR(window->WindowPadding.x * 0.5f);
-        window->DrawList->AddLine(ImVec2(separator_min_x, y), ImVec2(separator_max_x, y), col, 1.0f);
+        const float y = tab_bar->BarRect.Max.y;
+        window->DrawList->AddRectFilled(ImVec2(tab_bar->SeparatorMinX, y - g.Style.TabBarBorderSize), ImVec2(tab_bar->SeparatorMaxX, y), col);
     }
     return true;
 }
@@ -8787,7 +8790,7 @@ void ImGui::TabItemBackground(ImDrawList* draw_list, const ImRect& bb, ImGuiTabI
     IM_ASSERT(width > 0.0f);
     const float rounding = ImMax(0.0f, ImMin((flags & ImGuiTabItemFlags_Button) ? g.Style.FrameRounding : g.Style.TabRounding, width * 0.5f - 1.0f));
     const float y1 = bb.Min.y + 1.0f;
-    const float y2 = bb.Max.y - 1.0f;
+    const float y2 = bb.Max.y - g.Style.TabBarBorderSize;
     draw_list->PathLineTo(ImVec2(bb.Min.x, y2));
     draw_list->PathArcToFast(ImVec2(bb.Min.x + rounding, y1 + rounding), rounding, 6, 9);
     draw_list->PathArcToFast(ImVec2(bb.Max.x - rounding, y1 + rounding), rounding, 9, 12);