Separator: added and following style.SeparatorSize. (#2657, #9263)

Reapply c5d83d8a from 1.70 which was reverted in 9534ef9b2.

docs/CHANGELOG.txt

@@ -41,6 +41,18 @@ HOW TO UPDATE?
 
 Breaking Changes:
 
+ - Separator(): fixed a legacy quirk where Separator() was submitting a zero-height
+   item for layout purpose, even though it draws a 1-pixel separator.
+   The fix could affect code e.g. computing height from multiple widgets in order to
+   allocate vertical space for a footer or multi-line status bar. (#2657, #9263)
+   The "Console" example had such a bug:
+      float footer_height = style.ItemSpacing.y + ImGui::GetFrameHeightWithSpacing();
+      BeginChild("ScrollingRegion", { 0, -footer_height });
+   Should be:
+      float footer_height = style.ItemSpacing.y + style.SeparatorSize + ImGui::GetFrameHeightWithSpacing();
+      BeginChild("ScrollingRegion", { 0, -footer_height });
+   When such idiom was used and assuming zero-height Separator, it is likely that
+   in 1.92.7 the resulting window will have unexpected 1 pixel scrolling range.
  - Combo(), ListBox(): commented out legacy signatures which were obsoleted in 1.90
    (Nov 2023), when the getter callback type was changed from:
       getter type:   bool (*getter)(void* user_data, int idx, const char** out_text)
@@ -67,7 +79,8 @@ Other Changes:
     - InputText Caret/cursor thickness. (#7031)
     - CloseButton() thickness.
     - TextLink() underline thickness.
-    - ColorButton() border.
+    - ColorButton() border thickness.
+    - Separator() thickness, via scaling newly added style.SeparatorSize. (#2657, #9263)
 - Demo: fixed IMGUI_DEMO_MARKER locations for examples applets. (#9261, #3689) [@pthom]
 - Clipper:
   - Clear `DisplayStart`/`DisplayEnd` fields when `Step()` returns false.

imgui.cpp

@@ -394,7 +394,17 @@ IMPLEMENTING SUPPORT for ImGuiBackendFlags_RendererHasTextures:
  When you are not sure about an old symbol or function name, try using the Search/Find function of your IDE to look for comments or references in all imgui files.
  You can read releases logs https://github.com/ocornut/imgui/releases for more details.
 
- - 2026/02/27 (1.92.7) - Commented out legacy signature for Combo(), ListBox(), signatures which were obsoleted in 1.90 (Nov 2023), when the getter callback type was changed.
+ - 2026/02/26 (1.92.7) - Separator: fixed a legacy quirk where Separator() was submitting a zero-height item for layout purpose, even though it draws a 1-pixel separator.
+                         The fix could affect code e.g. computing height from multiple widgets in order to allocate vertical space for a footer or multi-line status bar. (#2657, #9263)
+                         The "Console" example had such a bug:
+                            float footer_height = style.ItemSpacing.y + ImGui::GetFrameHeightWithSpacing();
+                            BeginChild("ScrollingRegion", { 0, -footer_height });
+                         Should be:
+                            float footer_height = style.ItemSpacing.y + style.SeparatorSize + ImGui::GetFrameHeightWithSpacing();
+                            BeginChild("ScrollingRegion", { 0, -footer_height });
+   When such idiom was used and assuming zero-height Separator, it is likely that
+   in 1.92.7 the resulting window will have unexpected 1 pixel scrolling range.
+ - 2026/02/23 (1.92.7) - Commented out legacy signature for Combo(), ListBox(), signatures which were obsoleted in 1.90 (Nov 2023), when the getter callback type was changed.
                          - Old getter type:   bool (*getter)(void* user_data, int idx, const char** out_text)   // Set label + return bool. False replaced label with placeholder.
                          - New getter type:   const char* (*getter)(void* user_data, int idx)                   // Return label or NULL/empty label if missing
  - 2026/01/08 (1.92.6) - Commented out legacy names obsoleted in 1.90 (Sept 2023): 'BeginChildFrame()' --> 'BeginChild()' with 'ImGuiChildFlags_FrameStyle'. 'EndChildFrame()' --> 'EndChild()'. 'ShowStackToolWindow()' --> 'ShowIDStackToolWindow()'. 'IM_OFFSETOF()' --> 'offsetof()'.
@@ -1499,7 +1509,8 @@ ImGuiStyle::ImGuiStyle()
     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.
-    SeparatorTextBorderSize     = 3.0f;             // Thickness of border in SeparatorText()
+    SeparatorSize               = 1.0f;             // Thickness of border in Separator().
+    SeparatorTextBorderSize     = 3.0f;             // Thickness of border in SeparatorText().
     SeparatorTextAlign          = ImVec2(0.0f,0.5f);// Alignment of text within the separator. Defaults to (0.0f, 0.5f) (left aligned, center).
     SeparatorTextPadding        = ImVec2(20.0f,3.f);// Horizontal offset of text from each edge of the separator + spacing on other axis. Generally small values. .y is recommended to be == FramePadding.y.
     DisplayWindowPadding        = ImVec2(19,19);    // Window position are clamped to be visible within the display area or monitors by at least this amount. Only applies to regular windows.
@@ -1572,8 +1583,9 @@ void ImGuiStyle::ScaleAllSizes(float scale_factor)
     DragDropTargetBorderSize = ImTrunc(DragDropTargetBorderSize * scale_factor);
     DragDropTargetPadding = ImTrunc(DragDropTargetPadding * scale_factor);
     ColorMarkerSize = ImTrunc(ColorMarkerSize * scale_factor);
-    SeparatorTextPadding = ImTrunc(SeparatorTextPadding * scale_factor);
+    SeparatorSize = ImTrunc(SeparatorSize * scale_factor);
     SeparatorTextBorderSize = ImTrunc(SeparatorTextBorderSize * scale_factor);
+    SeparatorTextPadding = ImTrunc(SeparatorTextPadding * scale_factor);
     DisplayWindowPadding = ImTrunc(DisplayWindowPadding * scale_factor);
     DisplaySafeAreaPadding = ImTrunc(DisplaySafeAreaPadding * scale_factor);
     MouseCursorScale = ImTrunc(MouseCursorScale * scale_factor);
@@ -3636,6 +3648,7 @@ static const ImGuiStyleVarInfo GStyleVarsInfo[] =
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, TreeLinesRounding)},          // ImGuiStyleVar_TreeLinesRounding
     { 2, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, ButtonTextAlign) },           // ImGuiStyleVar_ButtonTextAlign
     { 2, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, SelectableTextAlign) },       // ImGuiStyleVar_SelectableTextAlign
+    { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, SeparatorSize)},              // ImGuiStyleVar_SeparatorSize
     { 1, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, SeparatorTextBorderSize)},    // ImGuiStyleVar_SeparatorTextBorderSize
     { 2, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, SeparatorTextAlign) },        // ImGuiStyleVar_SeparatorTextAlign
     { 2, ImGuiDataType_Float, (ImU32)offsetof(ImGuiStyle, SeparatorTextPadding) },      // ImGuiStyleVar_SeparatorTextPadding

imgui.h

@@ -30,7 +30,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM >= 12345')
 #define IMGUI_VERSION       "1.92.7 WIP"
-#define IMGUI_VERSION_NUM   19263
+#define IMGUI_VERSION_NUM   19264
 #define IMGUI_HAS_TABLE             // Added BeginTable() - from IMGUI_VERSION_NUM >= 18000
 #define IMGUI_HAS_TEXTURES          // Added ImGuiBackendFlags_RendererHasTextures - from IMGUI_VERSION_NUM >= 19198
 
@@ -1852,6 +1852,7 @@ enum ImGuiStyleVar_
     ImGuiStyleVar_TreeLinesRounding,        // float     TreeLinesRounding
     ImGuiStyleVar_ButtonTextAlign,          // ImVec2    ButtonTextAlign
     ImGuiStyleVar_SelectableTextAlign,      // ImVec2    SelectableTextAlign
+    ImGuiStyleVar_SeparatorSize,            // float     SeparatorSize
     ImGuiStyleVar_SeparatorTextBorderSize,  // float     SeparatorTextBorderSize
     ImGuiStyleVar_SeparatorTextAlign,       // ImVec2    SeparatorTextAlign
     ImGuiStyleVar_SeparatorTextPadding,     // ImVec2    SeparatorTextPadding
@@ -2331,6 +2332,7 @@ struct ImGuiStyle
     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.
+    float       SeparatorSize;              // Thickness of border in Separator()
     float       SeparatorTextBorderSize;    // Thickness of border in SeparatorText()
     ImVec2      SeparatorTextAlign;         // Alignment of text within the separator. Defaults to (0.0f, 0.5f) (left aligned, center).
     ImVec2      SeparatorTextPadding;       // Horizontal offset of text from each edge of the separator + spacing on other axis. Generally small values. .y is recommended to be == FramePadding.y.

imgui_demo.cpp

@@ -8507,6 +8507,7 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
             SameLine(); HelpMarker("Alignment applies when a button is larger than its text content.");
             SliderFloat2("SelectableTextAlign", (float*)&style.SelectableTextAlign, 0.0f, 1.0f, "%.2f");
             SameLine(); HelpMarker("Alignment applies when a selectable is larger than its text content.");
+            SliderFloat("SeparatorSize", &style.SeparatorSize, 0.0f, 10.0f, "%.0f");
             SliderFloat("SeparatorTextBorderSize", &style.SeparatorTextBorderSize, 0.0f, 10.0f, "%.0f");
             SliderFloat2("SeparatorTextAlign", (float*)&style.SeparatorTextAlign, 0.0f, 1.0f, "%.2f");
             SliderFloat2("SeparatorTextPadding", (float*)&style.SeparatorTextPadding, 0.0f, 40.0f, "%.0f");
@@ -8975,7 +8976,8 @@ struct ExampleAppConsole
         ImGui::Separator();
 
         // Reserve enough left-over height for 1 separator + 1 input text
-        const float footer_height_to_reserve = ImGui::GetStyle().ItemSpacing.y + ImGui::GetFrameHeightWithSpacing();
+        ImGuiStyle& style = ImGui::GetStyle();
+        const float footer_height_to_reserve = style.SeparatorSize + style.ItemSpacing.y + ImGui::GetFrameHeightWithSpacing();
         if (ImGui::BeginChild("ScrollingRegion", ImVec2(0, -footer_height_to_reserve), ImGuiChildFlags_NavFlattened, ImGuiWindowFlags_HorizontalScrollbar))
         {
             if (ImGui::BeginPopupContextWindow())

imgui_widgets.cpp

@@ -1664,9 +1664,13 @@ void ImGui::SeparatorEx(ImGuiSeparatorFlags flags, float thickness)
 
         // We don't provide our width to the layout so that it doesn't get feed back into AutoFit
         // FIXME: This prevents ->CursorMaxPos based bounding box evaluation from working (e.g. TableEndCell)
-        const float thickness_for_layout = (thickness == 1.0f) ? 0.0f : thickness; // FIXME: See 1.70/1.71 Separator() change: makes legacy 1-px separator not affect layout yet. Should change.
+
+        // Between 1.71 and 1.92.7, we maintained a hack where a 1.0f thin Separator() would not impact layout.
+        // This was mostly chosen to allow backward compatibility with user's code assuming zero-height when calculating height for layout (e.g. bottom alignment of a status bar).
+        // In order to handle scaling we need to scale separator thickness and it would not makes sense to have a disparity depending on height.
+        ////float thickness_for_layout = (thickness == 1.0f) ? 0.0f : thickness; // FIXME: See 1.70/1.71 Separator() change: makes legacy 1-px separator not affect layout yet. Should change.
         const ImRect bb(ImVec2(x1, window->DC.CursorPos.y), ImVec2(x2, window->DC.CursorPos.y + thickness));
-        ItemSize(ImVec2(0.0f, thickness_for_layout));
+        ItemSize(ImVec2(0.0f, thickness));
 
         if (ItemAdd(bb, 0))
         {
@@ -1692,14 +1696,13 @@ void ImGui::Separator()
         return;
 
     // Those flags should eventually be configurable by the user
-    // FIXME: We cannot g.Style.SeparatorTextBorderSize for thickness as it relates to SeparatorText() which is a decorated separator, not defaulting to 1.0f.
     ImGuiSeparatorFlags flags = (window->DC.LayoutType == ImGuiLayoutType_Horizontal) ? ImGuiSeparatorFlags_Vertical : ImGuiSeparatorFlags_Horizontal;
 
     // Only applies to legacy Columns() api as they relied on Separator() a lot.
     if (window->DC.CurrentColumns)
         flags |= ImGuiSeparatorFlags_SpanAllColumns;
 
-    SeparatorEx(flags, 1.0f);
+    SeparatorEx(flags, g.Style.SeparatorSize);
 }
 
 void ImGui::SeparatorTextEx(ImGuiID id, const char* label, const char* label_end, float extra_w)