Fix ImDrawList::AddImageRounded (#1994)

The function makes an assumption that there exists 1 font atlas texture,
so that `ImDrawList._Data->TexIdCommon` ==
`ImDrawList._CmdHeader.TextureId`. Since we support multiple font atlas
textures, that assumption is no longer true and
`ImDrawList::AddConvexPolyFilled` will create a new draw command as
needed, giving `ImGui::ShadeVertsLinearUV` a clean draw command to work
with.

This workaround forcefully sets *the* font atlas texture to be the
texture the user is trying to draw for the duration of drawing polygons
and shading those vertices again, so that no draw command change
happens. Once the operation is done, font atlas texture is reverted back
to what it was.

This fix is done without thread safety concerns, but an `ImDrawList`
should not be touched from multiple threads at a single time, so this is
fine.

Dalamud/Interface/Internal/ImGuiDrawListFixProvider.cs

@@ -28,10 +28,12 @@ internal sealed unsafe class ImGuiDrawListFixProvider : IInternalDisposableServi
 {
     private const int CImGuiImDrawListAddPolyLineOffset = 0x589B0;
     private const int CImGuiImDrawListAddRectFilled = 0x59FD0;
+    private const int CImGuiImDrawListAddImageRounded = 0x58390;
     private const int CImGuiImDrawListSharedDataTexIdCommonOffset = 0;
 
     private readonly Hook<ImDrawListAddPolyLine> hookImDrawListAddPolyline;
     private readonly Hook<ImDrawListAddRectFilled> hookImDrawListAddRectFilled;
+    private readonly Hook<ImDrawListAddImageRounded> hookImDrawListAddImageRounded;
 
     [ServiceManager.ServiceConstructor]
     private ImGuiDrawListFixProvider(InterfaceManager.InterfaceManagerWithScene imws)
@@ -48,8 +50,12 @@ private ImGuiDrawListFixProvider(InterfaceManager.InterfaceManagerWithScene imws
         this.hookImDrawListAddRectFilled = Hook<ImDrawListAddRectFilled>.FromAddress(
             cimgui + CImGuiImDrawListAddRectFilled,
             this.ImDrawListAddRectFilledDetour);
+        this.hookImDrawListAddImageRounded = Hook<ImDrawListAddImageRounded>.FromAddress(
+            cimgui + CImGuiImDrawListAddImageRounded,
+            this.ImDrawListAddImageRoundedDetour);
         this.hookImDrawListAddPolyline.Enable();
         this.hookImDrawListAddRectFilled.Enable();
+        this.hookImDrawListAddImageRounded.Enable();
     }
 
     private delegate void ImDrawListAddPolyLine(
@@ -68,11 +74,56 @@ private delegate void ImDrawListAddRectFilled(
         float rounding,
         ImDrawFlags flags);
 
+    private delegate void ImDrawListAddImageRounded(
+        ImDrawListPtr drawListPtr,
+        nint userTextureId,        ref Vector2 xy0,
+        ref Vector2 xy1,
+        ref Vector2 uv0,
+        ref Vector2 uv1,
+        uint col,
+        float rounding,
+        ImDrawFlags flags);
+
     /// <inheritdoc/>
     void IInternalDisposableService.DisposeService()
     {
         this.hookImDrawListAddPolyline.Dispose();
         this.hookImDrawListAddRectFilled.Dispose();
+        this.hookImDrawListAddImageRounded.Dispose();
+    }
+
+    private static ImDrawFlags FixRectCornerFlags(ImDrawFlags flags)
+    {
+#if !IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+        // Legacy Support for hard coded ~0 (used to be a suggested equivalent to ImDrawCornerFlags_All)
+        //   ~0   --> ImDrawFlags_RoundCornersAll or 0
+        if ((int)flags == ~0)
+            return ImDrawFlags.RoundCornersAll;
+
+        // Legacy Support for hard coded 0x01 to 0x0F (matching 15 out of 16 old flags combinations)
+        //   0x01 --> ImDrawFlags_RoundCornersTopLeft (VALUE 0x01 OVERLAPS ImDrawFlags_Closed but ImDrawFlags_Closed is never valid in this path!)
+        //   0x02 --> ImDrawFlags_RoundCornersTopRight
+        //   0x03 --> ImDrawFlags_RoundCornersTopLeft | ImDrawFlags_RoundCornersTopRight
+        //   0x04 --> ImDrawFlags_RoundCornersBotLeft
+        //   0x05 --> ImDrawFlags_RoundCornersTopLeft | ImDrawFlags_RoundCornersBotLeft
+        //   ...
+        //   0x0F --> ImDrawFlags_RoundCornersAll or 0
+        // (See all values in ImDrawCornerFlags_)
+        if ((int)flags >= 0x01 && (int)flags <= 0x0F)
+            return (ImDrawFlags)((int)flags << 4);
+
+        // We cannot support hard coded 0x00 with 'float rounding > 0.0f' --> replace with ImDrawFlags_RoundCornersNone or use 'float rounding = 0.0f'
+#endif
+
+        // If this triggers, please update your code replacing hardcoded values with new ImDrawFlags_RoundCorners* values.
+        // Note that ImDrawFlags_Closed (== 0x01) is an invalid flag for AddRect(), AddRectFilled(), PathRect() etc...
+        if (((int)flags & 0x0F) != 0)
+            throw new ArgumentException("Misuse of legacy hardcoded ImDrawCornerFlags values!");
+
+        if ((flags & ImDrawFlags.RoundCornersMask) == 0)
+            flags |= ImDrawFlags.RoundCornersAll;
+
+        return flags;
     }
 
     private void ImDrawListAddRectFilledDetour(
@@ -130,4 +181,42 @@ private void ImDrawListAddPolylineDetour(
         if (pushTextureId)
             drawListPtr.PopTextureID();
     }
+
+    private void ImDrawListAddImageRoundedDetour(ImDrawListPtr drawListPtr, nint userTextureId, ref Vector2 xy0, ref Vector2 xy1, ref Vector2 uv0, ref Vector2 uv1, uint col, float rounding, ImDrawFlags flags)
+    {
+        // Skip drawing if we're drawing something with alpha value of 0.
+        if ((col & 0xFF000000) == 0)
+            return;
+
+        // Handle non-rounded cases.
+        flags = FixRectCornerFlags(flags);
+        if (rounding < 0.5f || (flags & ImDrawFlags.RoundCornersMask) == ImDrawFlags.RoundCornersNone)
+        {
+            drawListPtr.AddImage(userTextureId, xy0, xy1, uv0, uv1, col);
+            return;
+        }
+
+        // Temporary provide the requested image as the common texture ID, so that the underlying
+        // ImDrawList::AddConvexPolyFilled does not create a separate draw command and then revert back.
+        // ImDrawList::AddImageRounded will temporarily push the texture ID provided by the user if the latest draw
+        // command does not point to the texture we're trying to draw. Once pushed, ImDrawList::AddConvexPolyFilled
+        // will leave the list of draw commands alone, so that ImGui::ShadeVertsLinearUV can safely work on the latest
+        // draw command.
+        ref var texIdCommon = ref *(nint*)(drawListPtr._Data + CImGuiImDrawListSharedDataTexIdCommonOffset);
+        var texIdCommonPrev = texIdCommon;
+        texIdCommon = userTextureId;
+
+        this.hookImDrawListAddImageRounded.Original(
+            drawListPtr,
+            texIdCommon,
+            ref xy0,
+            ref xy1,
+            ref uv0,
+            ref uv1,
+            col,
+            rounding,
+            flags);
+
+        texIdCommon = texIdCommonPrev;
+    }
 }