Attachment 301744 Details for Bug 154283 – Patch

[patch] Patch

bug-154283-20170216134652.patch (text/plain), 7.94 KB, created by Miguel Gomez on 2017-02-16 04:49:30 PST

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Creator: Miguel Gomez

Created: 2017-02-16 04:49:30 PST

Size: 7.94 KB

patch

obsolete

>Subversion Revision: 212427
>diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
>index 8c99faa29c30fe31ef0f691a496ca0efcc13a6ba..7e71294164b0a1c37f775eb26bd01135a13eb627 100644
>--- a/Source/WebCore/ChangeLog
>+++ b/Source/WebCore/ChangeLog
>@@ -1,3 +1,28 @@
>+2017-02-16  Miguel Gomez  <magomez@igalia.com>
>+
>+        [GTK] scroll with transparent background not repainted after scrollY >= 32768
>+        https://bugs.webkit.org/show_bug.cgi?id=154283
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        Due to a limitation of the pixman backend, which uses 16 bits to hold signed integers, cairo is
>+        not able to draw anything when using transformation matrices with values bigger than 32768. When
>+        drawing patterns into large pages, the matrices values can overflow those 16 bits, so cairo doesn't
>+        draw anything in, which causes the reported transparent backgrounds.
>+
>+        The patch modifies the transformation matrices both from the current context and the pattern we
>+        are painting, to avoid them to hold values that cannot stored in 16 bits.
>+
>+        There's still the possibility that this happens, but it would require using a pattern with a size
>+        bigger than 32768.
>+
>+        Based on a previous patch by Gwang Yoon Hwang  <yoon@igalia.com>.
>+
>+        Test: fast/backgrounds/background-repeat-long-scroll.html
>+
>+        * platform/graphics/cairo/CairoUtilities.cpp:
>+        (WebCore::drawPatternToCairoContext):
>+
> 2017-02-15  Jer Noble  <jer.noble@apple.com>
> 
>         REGRESSION (r212311): NULL-dereference in HTMLMediaElement::prepareToPlay()
>diff --git a/Source/WebCore/platform/graphics/cairo/CairoUtilities.cpp b/Source/WebCore/platform/graphics/cairo/CairoUtilities.cpp
>index fc485894014f2d2d0baa2893989b13934ba2a7d6..1fd51d76e774f1d83b9bef4710707a4c4483c568 100644
>--- a/Source/WebCore/platform/graphics/cairo/CairoUtilities.cpp
>+++ b/Source/WebCore/platform/graphics/cairo/CairoUtilities.cpp
>@@ -205,8 +205,46 @@ void drawPatternToCairoContext(cairo_t* cr, cairo_surface_t* image, const IntSiz
>     cairo_pattern_t* pattern = cairo_pattern_create_for_surface(image);
>     cairo_pattern_set_extend(pattern, CAIRO_EXTEND_REPEAT);
> 
>+    // Due to a limitation in pixman, cairo cannot handle transformation matrices with values bigger than 32768. If the value is
>+    // bigger, cairo is not able to paint anything, and this is the reason for the missing backgrounds reported in
>+    // https://bugs.webkit.org/show_bug.cgi?id=154283.
>+
>+    // When drawing a pattern there are 2 matrices that can overflow this limitation, and they are the current transformation
>+    // matrix (which translates user space coordinates to coordinates of the output device) and the pattern matrix (which translates
>+    // user space coordinates to pattern coordinates). The overflow happens only in the translation components of the matrices.
>+
>+    // To avoid the problem in the transformation matrix what we do is remove the translation components of the transformation matrix
>+    // and perform the translation by moving the destination rectangle instead. For this, we get its translation components (which are in
>+    // device coordinates) and divide them by the scale factor to take them to user space coordinates. Then we move the transformation
>+    // matrix by the opposite of that amount (which will zero the translation components of the transformation matrix), and move
>+    // the destination rectangle by the same amount. We also need to apply the same translation to the pattern matrix, so we get the
>+    // same pattern coordinates for the new destination rectangle.
>+
>+    cairo_matrix_t ctm;
>+    cairo_get_matrix(cr, &ctm);
>+    double dx = 0, dy = 0;
>+    cairo_matrix_transform_point(&ctm, &dx, &dy);
>+    double xScale = 1, yScale = 1;
>+    cairo_matrix_transform_distance(&ctm, &xScale, &yScale);
>+
>+    dx = dx / xScale;
>+    dy = dy / yScale;
>+    cairo_translate(cr, -dx, -dy);
>+    FloatRect adjustedDestRect(destRect);
>+    adjustedDestRect.move(dx, dy);
>+
>+    // Regarding the pattern matrix, what we do is reduce the translation component of the matrix taking advantage of the fact that we
>+    // are drawing a repeated pattern. This means that, assuming that (w, h) is the size of the pattern, samplig it at (x, y) is the same
>+    // than sampling it at (x mod w, y mod h), so we transform the translation component of the pattern matrix in that way.
>+
>     cairo_matrix_t patternMatrix = cairo_matrix_t(patternTransform);
>-    cairo_matrix_t phaseMatrix = {1, 0, 0, 1, phase.x() + tileRect.x() * patternTransform.a(), phase.y() + tileRect.y() * patternTransform.d()};
>+    // dx and dy are added here as well to compensate the previous translation of the destination rectangle.
>+    double phaseOffsetX = phase.x() + tileRect.x() * patternTransform.a() + dx;
>+    double phaseOffsetY = phase.y() + tileRect.y() * patternTransform.d() + dy;
>+    // this is where we perform the (x mod w, y mod h) metioned above, but with floats instead of integers.
>+    phaseOffsetX -= std::trunc(phaseOffsetX / (tileRect.width() * patternTransform.a())) * tileRect.width() * patternTransform.a();
>+    phaseOffsetY -= std::trunc(phaseOffsetY / (tileRect.height() * patternTransform.d())) * tileRect.height() * patternTransform.d();
>+    cairo_matrix_t phaseMatrix = {1, 0, 0, 1, phaseOffsetX, phaseOffsetY};
>     cairo_matrix_t combined;
>     cairo_matrix_multiply(&combined, &patternMatrix, &phaseMatrix);
>     cairo_matrix_invert(&combined);
>@@ -215,7 +253,7 @@ void drawPatternToCairoContext(cairo_t* cr, cairo_surface_t* image, const IntSiz
>     cairo_set_operator(cr, op);
>     cairo_set_source(cr, pattern);
>     cairo_pattern_destroy(pattern);
>-    cairo_rectangle(cr, destRect.x(), destRect.y(), destRect.width(), destRect.height());
>+    cairo_rectangle(cr, adjustedDestRect.x(), adjustedDestRect.y(), adjustedDestRect.width(), adjustedDestRect.height());
>     cairo_fill(cr);
> 
>     cairo_restore(cr);
>diff --git a/LayoutTests/ChangeLog b/LayoutTests/ChangeLog
>index d5a53e406d39d860d2c0aa69f4a5ac3a7f41fb38..b6a0cb74b5cccde3187a3b406210e264d9c746b3 100644
>--- a/LayoutTests/ChangeLog
>+++ b/LayoutTests/ChangeLog
>@@ -1,3 +1,16 @@
>+2017-02-16  Miguel Gomez  <magomez@igalia.com>
>+
>+        [GTK] scroll with transparent background not repainted after scrollY >= 32768
>+        https://bugs.webkit.org/show_bug.cgi?id=154283
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        Test to ensure that the background pattern of an element is properly being drawn when it's in a position
>+        bigger than 32768.
>+
>+        * fast/backgrounds/background-repeat-long-scroll-expected.html: Added.
>+        * fast/backgrounds/background-repeat-long-scroll.html: Added.
>+
> 2017-02-15  Ryan Haddad  <ryanhaddad@apple.com>
> 
>         Mark inspector/debugger/search-scripts.html as flaky.
>diff --git a/LayoutTests/fast/backgrounds/background-repeat-long-scroll-expected.html b/LayoutTests/fast/backgrounds/background-repeat-long-scroll-expected.html
>new file mode 100644
>index 0000000000000000000000000000000000000000..7672bd57c35eec150cf29f5df6cf5cdf467d5db8
>--- /dev/null
>+++ b/LayoutTests/fast/backgrounds/background-repeat-long-scroll-expected.html
>@@ -0,0 +1,16 @@
>+<!DOCTYPE html>
>+<html>
>+<head>
>+<style>
>+#div1 {
>+background-color: black;
>+width: 100%;
>+height: 35000px;
>+}
>+</style>
>+</head>
>+<body onload="window.scrollTo(0,34000)">
>+<div id="div1">
>+</div>
>+</body>
>+</html>
>\ No newline at end of file
>diff --git a/LayoutTests/fast/backgrounds/background-repeat-long-scroll.html b/LayoutTests/fast/backgrounds/background-repeat-long-scroll.html
>new file mode 100644
>index 0000000000000000000000000000000000000000..7106447c8bd96aa823b213e267873ab993f6dda0
>--- /dev/null
>+++ b/LayoutTests/fast/backgrounds/background-repeat-long-scroll.html
>@@ -0,0 +1,16 @@
>+<!DOCTYPE html>
>+<html>
>+<head>
>+<style>
>+#div1 {
>+background: url('./resources/black25x25.png') left top repeat;
>+width: 100%;
>+height: 35000px;
>+}
>+</style>
>+</head>
>+<body onload="window.scrollTo(0,34000)">
>+<div id="div1">
>+</div>
>+</body>
>+</html>
>\ No newline at end of file

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Attachments on bug 154283: 271986 | 272084 | 277862 | 301043 | 301047 | 301051 | 301744