Safeguard against very large Bitmap creation #2662
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Because we rely on the transform `Matrix` returned from the `Canvas` to size a `Bitmap` when using software rendering, an erroneous matrix value can cause a very large Bitmap to be allocated, triggering an OutOfMemory exception. We've encountered such a situation when using `layoutlib` for screenshot tests, which uses a `NopCanvas` [on initial render](https://cs.android.com/android/_/android/platform/frameworks/layoutlib/+/7b05b277beee599532606e9bb6d7a71f5ca2ab6e:bridge/src/com/android/layoutlib/bridge/impl/RenderSessionImpl.java;l=543;bpv=1;bpt=0;drc=085857f145aac790e2a08cf6eb9546f98e26c338) that can return an invalid `Matrix.
gpeal
reviewed
Sep 25, 2025
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| if (renderWidth <= 0 || renderHeight <= 0) { | ||
| // Safeguard against errors during Bitmap creation by returning early if dimensions are invalid. | ||
| if (renderWidth <= 0 || renderHeight <= 0 || renderWidth > bounds.width() || renderHeight > bounds.height()) { |
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Wouldn't this not render an image if it scaled up so it covered the whole screen + 1px?
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In that case can we clip the bounds so that we only allocate a bitmap large enough to draw what's shown onscreen?
I'm trying to guard against cases where the Canvas matrix returns an invalid scale or translation that causes something like a 1,000,000 x 1,000,000 bitmap to be allocated.
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Could you take a look at the snapshot tests? Looks like there are a bunch of blanks now. |
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Because we rely on the transform
Matrixreturned from theCanvasto size aBitmapwhen using software rendering, an erroneous matrix value can cause a very large Bitmap to be allocated, triggering an OutOfMemory exception.We've encountered such a situation when using
layoutlibfor screenshot tests, which uses aNopCanvason initial render that can return an invalid `Matrix.