[PATCH 1/1] gdiplus: Clip polygons before drawing them

[David Kahurani]

From: David Kahurani

This should reduce the load on GDI when an application is trying to
draw to regions outside of selected DC's region

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=41617
Signed-off-by: David Kahurani 
---
 dlls/gdiplus/graphics.c | 93 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)

diff --git a/dlls/gdiplus/graphics.c b/dlls/gdiplus/graphics.c
index 835c2889bd1..7475557280c 100644
--- a/dlls/gdiplus/graphics.c
+++ b/dlls/gdiplus/graphics.c
@@ -1920,6 +1920,98 @@ static void shorten_bezier_amt(GpPointF * pt, REAL amt, BOOL rev)
     }
 }

+static void poly_clip(GpGraphics *graphics, POINT *pti, BYTE *tp, int count)
+{
+    RectF rect;
+    BITMAP structBitmapHeader = {0};
+    HGDIOBJ hBitmap = GetCurrentObject(graphics->hdc, OBJ_BITMAP);
+    BYTE *tpcopy = malloc(count);
+
+    memcpy(tpcopy, tp, count);
+    GetObjectW(hBitmap, sizeof(BITMAP), &structBitmapHeader);
+    set_rect(&rect, 0, 0, structBitmapHeader.bmWidth, structBitmapHeader.bmHeight);
+
+    /* Ignore data that is not meant for drawing */
+    if (rect.Width == 1 && rect.Height == 1)
+        return;
+
+    /* DC attributes were not set, assume client area */
+    if (rect.Width == 0 && rect.Height == 0)
+    {
+        RECT lpRect;
+        GetClientRect(graphics->hwnd, &lpRect);
+        rect.Width = lpRect.right;
+        rect.Height = lpRect.bottom;
+    }
+
+    for (int i = 0; i < count; i++)
+    {
+         switch(tp[i] &~ PT_CLOSEFIGURE)
+         {
+         case PT_BEZIERTO:
+         {
+             int j;
+
+             for (j = 0; j < 3; j++)
+             {
+                  REAL x = pti[i + j].x;
+                  REAL y = pti[i + j].y;
+
+                  /* At least part of the rectangle encompassing the bezier lies within the DC's region */
+                  if (rect.X <= x && rect.Y <= y && x <= rect.X + rect.Width && y <= rect.Y + rect.Height)
+                      break;
+             }
+
+             if (j == 3)
+             {
+                 for(j = 0; j < 3; j++)
+                     tp[i + j] = PT_MOVETO;
+             }
+
+             i += 2;
+             break;
+         }
+         case PT_LINETO:
+         {
+             int x1, y1, x2 = pti[i].x, y2 = pti[i].y;
+
+             if (i == 0)
+             {
+                 x1 = y1 = 0;
+             }
+             else
+             {
+                 x1 = pti[i - 1].x;
+                 y1 = pti[i - 1].y;
+             }
+
+             /* If any of the connecting points lies within DC's region */
+             if ((rect.X <= x1 && rect.Y <= y1 && x1 <= rect.X + rect.Width && y1 <= rect.Y + rect.Height) ||
+                 (rect.X <= x2 && rect.Y <= y2 && x2 <= rect.X + rect.Width && y2 <= rect.Y + rect.Height))
+             {
+                 if (i != 0)
+                 {
+                     tp[i - 1] = tpcopy[i - 1];
+                     tp[i] = tpcopy[i];
+                 }
+                 break;
+             }
+
+             tp[i] = PT_MOVETO;
+
+             break;
+         }
+         case PT_MOVETO:
+             break;
+
+         default:
+             ERR("Bad point type \n");
+         }
+    }
+
+    free(tpcopy);
+}
+
 /* Draws a combination of bezier curves and lines between points. */
 static GpStatus draw_poly(GpGraphics *graphics, GpPen *pen, GDIPCONST GpPointF * pt,
     GDIPCONST BYTE * types, INT count, BOOL caps)
@@ -2036,6 +2128,7 @@ static GpStatus draw_poly(GpGraphics *graphics, GpPen *pen, GDIPCONST GpPointF *
         tp[i] = convert_path_point_type(types[i]);
     }

+    poly_clip(graphics, pti, tp, count);
     PolyDraw(graphics->hdc, pti, tp, count);

status = Ok;