body.style.zoom of about 350% or higher with side panels can cause "BitmapImpl has invalid row_bytes for configuration" crash #541
Description
I changed my app to have side panels, so there is a leftpanel, centerpanel, and rightpanel. When the center and right panels are showing, and I set the body.style.zoom to about 350% or higher, Ultralight crashes:
Check Failed: row_bytes >= (width_ * bpp_) @ C:\Users\ajs15\dev\Ultralight-SDK-trunk\deps\UltralightCore-src\src\Ultralight\Bitmap.cc (255) BitmapImpl has invalid row_bytes for configuration
It happens when using either grid layout or float:left for the panels. I had ChatGPT make me a test page but it wouldn't happen with that in the UL sample browser.
ChatGPT says:
Ultralight is trying to allocate a bitmap for a render surface (usually a layer or paint buffer), but the row stride (row_bytes) computed from zoomed layout math ended up smaller than the actual pixel width × bytes-per-pixel (bpp).
That happens when the computed layout width overflows (wraps around) an integer boundary or rounds incorrectly at high zoom — most often due to one of these:
- Zoom > ~350% causes body.style.zoom to multiply clientWidth enough that a layout width > 16384 pixels (or similar internal limit) occurs.
- Subpixel rounding or a negative value sneaks in after scaling, leading to a mismatch between width_ and row_bytes.
- One of the panels (often right panel) ends up computed with a slightly negative or zero width due to floating-point rounding under zoom.