Add unit test for unbalanced save and restores in pictures.

R=reed@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/150653010

git-svn-id: http://skia.googlecode.com/svn/trunk@13430 2bbb7eff-a529-9590-31e7-b0007b416f81

include/core/SkCanvas.h

@@ -302,13 +302,15 @@ public:
     virtual void restore();
 
     /** Returns the number of matrix/clip states on the SkCanvas' private stack.
-        This will equal # save() calls - # restore() calls.
+        This will equal # save() calls - # restore() calls + 1. The save count on
+        a new canvas is 1.
     */
     int getSaveCount() const;
 
     /** Efficient way to pop any calls to save() that happened after the save
-        count reached saveCount. It is an error for saveCount to be less than
-        getSaveCount()
+        count reached saveCount. It is an error for saveCount to be greater than
+        getSaveCount(). To pop all the way back to the initial matrix/clip context
+        pass saveCount == 1.
         @param saveCount    The number of save() levels to restore from
     */
     void restoreToCount(int saveCount);

tests/PictureTest.cpp

@@ -680,6 +680,62 @@ static void rand_op(SkCanvas* canvas, SkRandom& rand) {
     }
 }
 
+static void set_canvas_to_save_count_4(SkCanvas* canvas) {
+    canvas->restoreToCount(1);
+    canvas->save();
+    canvas->save();
+    canvas->save();
+}
+
+static void test_unbalanced_save_restores(skiatest::Reporter* reporter) {
+    SkCanvas testCanvas(100, 100);
+    set_canvas_to_save_count_4(&testCanvas);
+
+    REPORTER_ASSERT(reporter, 4 == testCanvas.getSaveCount());
+
+    SkPaint paint;
+    SkRect rect = SkRect::MakeLTRB(-10000000, -10000000, 10000000, 10000000);
+
+    SkPicture extra_save_picture;
+    extra_save_picture.beginRecording(100, 100);
+    extra_save_picture.getRecordingCanvas()->save();
+    extra_save_picture.getRecordingCanvas()->translate(10, 10);
+    extra_save_picture.getRecordingCanvas()->drawRect(rect, paint);
+    extra_save_picture.getRecordingCanvas()->save();
+    extra_save_picture.getRecordingCanvas()->translate(10, 10);
+    extra_save_picture.getRecordingCanvas()->drawRect(rect, paint);
+
+    testCanvas.drawPicture(extra_save_picture);
+    REPORTER_ASSERT(reporter, 4 == testCanvas.getSaveCount());
+
+    set_canvas_to_save_count_4(&testCanvas);
+
+    SkPicture extra_restore_picture;
+    extra_restore_picture.beginRecording(100, 100);
+    extra_restore_picture.getRecordingCanvas()->save();
+    extra_restore_picture.getRecordingCanvas()->translate(10, 10);
+    extra_restore_picture.getRecordingCanvas()->drawRect(rect, paint);
+    extra_restore_picture.getRecordingCanvas()->save();
+    extra_restore_picture.getRecordingCanvas()->translate(10, 10);
+    extra_restore_picture.getRecordingCanvas()->drawRect(rect, paint);
+    extra_restore_picture.getRecordingCanvas()->restore();
+    extra_restore_picture.getRecordingCanvas()->restore();
+    extra_restore_picture.getRecordingCanvas()->restore();
+    extra_restore_picture.getRecordingCanvas()->restore();
+
+    testCanvas.drawPicture(extra_save_picture);
+    REPORTER_ASSERT(reporter, 4 == testCanvas.getSaveCount());
+
+    SkPicture no_save_picture;
+    extra_restore_picture.beginRecording(100, 100);
+    extra_restore_picture.getRecordingCanvas()->translate(10, 10);
+    extra_restore_picture.getRecordingCanvas()->drawRect(rect, paint);
+
+    testCanvas.drawPicture(extra_save_picture);
+    REPORTER_ASSERT(reporter, 4 == testCanvas.getSaveCount());
+    REPORTER_ASSERT(reporter, testCanvas.getTotalMatrix().isIdentity());
+}
+
 static void test_peephole() {
     SkRandom rand;
 
@@ -1021,6 +1077,7 @@ DEF_TEST(Picture, reporter) {
 #else
     test_bad_bitmap();
 #endif
+    test_unbalanced_save_restores(reporter);
     test_peephole();
     test_gatherpixelrefs(reporter);
     test_gatherpixelrefsandrects(reporter);