Fix Agg extent calculations for empty draws

dstansby · dstansby · commit 2a010391fd7d · 2018-09-15T11:57:55.000+01:00
diff --git a/src/_backend_agg.cpp b/src/_backend_agg.cpp
@@ -201,10 +201,15 @@ agg::rect_i RendererAgg::get_content_extents()
         }
     }
 
-    r.x1 = std::max(0, r.x1);
-    r.y1 = std::max(0, r.y1);
-    r.x2 = std::min(r.x2 + 1, (int)width);
-    r.y2 = std::min(r.y2 + 1, (int)height);
+    if (r.x1 == width && r.x2 == 0) {
+      // The buffer is completely empty.
+      r.x1 = r.y1 = r.x2 = r.y2 = 0;
+    } else {
+      r.x1 = std::max(0, r.x1);
+      r.y1 = std::max(0, r.y1);
+      r.x2 = std::min(r.x2 + 1, (int)width);
+      r.y2 = std::min(r.y2 + 1, (int)height);
+    }
 
     return r;
 }

Original file line number	Diff line number	Diff line change
`@@ -201,10 +201,15 @@ agg::rect_i RendererAgg::get_content_extents()`
`201`	`201`	`}`
`202`	`202`	`}`
`203`	`203`
`204`		`- r.x1 = std::max(0, r.x1);`
`205`		`- r.y1 = std::max(0, r.y1);`
`206`		`- r.x2 = std::min(r.x2 + 1, (int)width);`
`207`		`- r.y2 = std::min(r.y2 + 1, (int)height);`
	`204`	`+ if (r.x1 == width && r.x2 == 0) {`
	`205`	`+ // The buffer is completely empty.`
	`206`	`+ r.x1 = r.y1 = r.x2 = r.y2 = 0;`
	`207`	`+ } else {`
	`208`	`+ r.x1 = std::max(0, r.x1);`
	`209`	`+ r.y1 = std::max(0, r.y1);`
	`210`	`+ r.x2 = std::min(r.x2 + 1, (int)width);`
	`211`	`+ r.y2 = std::min(r.y2 + 1, (int)height);`
	`212`	`+ }`
`208`	`213`
`209`	`214`	`return r;`
`210`	`215`	`}`