ImDrawList: added InitialFringeScale in ImDrawListSharedData. Default to 1.0f.

This is to allow some DPI mods with less changes. Only the initial value in SetupDrawListSharedData() will need change.

imgui.cpp

@@ -5136,6 +5136,7 @@ static void SetupDrawListSharedData()
         g.DrawListSharedData.InitialFlags |= ImDrawListFlags_AntiAliasedFill;
     if (g.IO.BackendFlags & ImGuiBackendFlags_RendererHasVtxOffset)
         g.DrawListSharedData.InitialFlags |= ImDrawListFlags_AllowVtxOffset;
+    g.DrawListSharedData.InitialFringeScale = 1.0f; // FIXME-DPI: Change this for some DPI scaling experiments.
 }
 
 void ImGui::NewFrame()

imgui_draw.cpp

@@ -374,6 +374,7 @@ void ImGui::StyleColorsLight(ImGuiStyle* dst)
 ImDrawListSharedData::ImDrawListSharedData()
 {
     memset(this, 0, sizeof(*this));
+    InitialFringeScale = 1.0f;
     for (int i = 0; i < IM_ARRAYSIZE(ArcFastVtx); i++)
     {
         const float a = ((float)i * 2 * IM_PI) / (float)IM_ARRAYSIZE(ArcFastVtx);
@@ -433,7 +434,7 @@ void ImDrawList::_ResetForNewFrame()
     _Path.resize(0);
     _Splitter.Clear();
     CmdBuffer.push_back(ImDrawCmd());
-    _FringeScale = 1.0f;
+    _FringeScale = _Data->InitialFringeScale;
 }
 
 void ImDrawList::_ClearFreeMemory()

imgui_internal.h

@@ -786,8 +786,9 @@ struct IMGUI_API ImDrawListSharedData
     float           FontScale;                  // Current/default font scale (== FontSize / Font->FontSize)
     float           CurveTessellationTol;       // Tessellation tolerance when using PathBezierCurveTo()
     float           CircleSegmentMaxError;      // Number of circle segments to use per pixel of radius for AddCircle() etc
-    ImVec4          ClipRectFullscreen;         // Value for PushClipRectFullscreen()
+    float           InitialFringeScale;         // Initial scale to apply to AA fringe
     ImDrawListFlags InitialFlags;               // Initial flags at the beginning of the frame (it is possible to alter flags on a per-drawlist basis afterwards)
+    ImVec4          ClipRectFullscreen;         // Value for PushClipRectFullscreen()
     ImVector<ImVec2> TempBuffer;                // Temporary write buffer
 
     // Lookup tables

imgui_widgets.cpp

@@ -913,7 +913,7 @@ ImRect ImGui::GetWindowScrollbarRect(ImGuiWindow* window, ImGuiAxis axis)
     const ImRect outer_rect = window->Rect();
     const ImRect inner_rect = window->InnerRect;
     const float scrollbar_size = window->ScrollbarSizes[axis ^ 1]; // (ScrollbarSizes.x = width of Y scrollbar; ScrollbarSizes.y = height of X scrollbar)
-    IM_ASSERT(scrollbar_size > 0.0f);
+    IM_ASSERT(scrollbar_size >= 0.0f);
     const float border_size = IM_ROUND(window->WindowBorderSize * 0.5f);
     const float border_top = (window->Flags & ImGuiWindowFlags_MenuBar) ? IM_ROUND(g.Style.FrameBorderSize * 0.5f) : 0.0f;
     if (axis == ImGuiAxis_X)