[Webkit-unassigned] [Bug 61859] New: Out of memory when drawing text shadow for scale < 1.0

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=61859

           Summary: Out of memory when drawing text shadow for scale < 1.0
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: Platform
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: mariusz.g at samsung.com


Created an attachment (id=95593)
 --> (https://bugs.webkit.org/attachment.cgi?id=95593&action=review)
Web page: Korean text with shadow property

When drawing text shadow in EFL port(EWebLauncher) out of memory occurs.
Steps to reproduce: run EWebLauncher with attached file, zoom out, OOM occurs.

The problem is that for shadowed text(e.g. in attachment) font data for some glyphs is different than for first. In this case drawGlyphs() function is invoked(FontFastPath.cpp, line 387).

374    void Font::drawGlyphBuffer(GraphicsContext* context, const GlyphBuffer& glyphBuffer, const FloatPoint& point) const
375    {   
376        // Draw each contiguous run of glyphs that use the same font data.
377        const SimpleFontData* fontData = glyphBuffer.fontDataAt(0);
378        FloatSize offset = glyphBuffer.offsetAt(0);
379        FloatPoint startPoint(point);
380        float nextX = startPoint.x();
381        int lastFrom = 0;
382        int nextGlyph = 0;
383        while (nextGlyph < glyphBuffer.size()) {
384            const SimpleFontData* nextFontData = glyphBuffer.fontDataAt(nextGlyph);
385            FloatSize nextOffset = glyphBuffer.offsetAt(nextGlyph);
386            if (nextFontData != fontData || nextOffset != offset) {  /// <-------------------------------------------
387                drawGlyphs(context, fontData, glyphBuffer, lastFrom, nextGlyph - lastFrom, startPoint);
388    
389                lastFrom = nextGlyph;
390                fontData = nextFontData;
391                offset = nextOffset;
392                startPoint.setX(nextX);
393            }
394            nextX += glyphBuffer.advanceAt(nextGlyph);
395            nextGlyph++;
396        }
397    
398        drawGlyphs(context, fontData, glyphBuffer, lastFrom, nextGlyph - lastFrom, startPoint);
399    }

Than path is as below:
FontCairo.cpp: drawGlyphs()->drawGlyphsShadow()->beginShadowLayer()
ContextShadowCairo.cpp: beginShadowLayer()->adjustBlurDistance()

86    PlatformContext ContextShadow::beginShadowLayer(GraphicsContext* context, const FloatRect& layerArea)
87    {
88        adjustBlurDistance(context);
89    
90        double x1, x2, y1, y2;
91        cairo_clip_extents(context->platformContext()->cr(), &x1, &y1, &x2, &y2);
92        IntRect layerRect = calculateLayerBoundingRect(context, layerArea, IntRect(x1, y1, x2 - x1, y2 - y1));
93    
94        // Don't paint if we are totally outside the clip region.
95        if (layerRect.isEmpty())
96            return 0;
97    
98        m_layerImage = getScratchBuffer(layerRect.size());
99        m_layerContext = cairo_create(m_layerImage);
100    
101        // Always clear the surface first.
102        cairo_set_operator(m_layerContext, CAIRO_OPERATOR_CLEAR);
103        cairo_paint(m_layerContext);
104        cairo_set_operator(m_layerContext, CAIRO_OPERATOR_OVER);
105    
106        cairo_translate(m_layerContext, m_layerContextTranslation.x(), m_layerContextTranslation.y());
107        return m_layerContext;
108    }


181    void ContextShadow::adjustBlurDistance(GraphicsContext* context)
182    {
183        const AffineTransform transform = context->getCTM();
184    
185        // Adjust blur if we're scaling, since the radius must not be affected by transformations.
186        if (transform.isIdentity())
187            return;
188    
........................
206        m_blurDistance = roundf(static_cast<float>(m_blurDistance) / scale);
207    }

Using m_blurDistance size of cairo context is calculated. 
For GTK port there is no transformation set on cairo, so transform.isIdentity() always returns true(only because of it OOM doesn't occur in GTK). But for EFL port when zoom is done following function(ewk_view.cpp) is invoked, which changes cairo_matrix.

3324    void ewk_view_paint_context_translate(Ewk_View_Paint_Context* ctxt, float x, float y)
3325    {
3326        EINA_SAFETY_ON_NULL_RETURN(ctxt);
3327    
3328        ctxt->gc->translate(x, y);
3329    }

In this for scale < 1.0 m_blurDistance is calculated as, e.g. for 0.5
m_blurDistance = m_blurDistance/0.5 several times, so this distance growths and growths, and cairo context is tried to be created for greater and greater rectangle, and at the end out of memory condition occurs.

-- 
Configure bugmail: https://bugs.webkit.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.