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fix: handle fractional device pixel ratio in Emscripten #168

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Merged
treeform merged 4 commits into from
Mar 18, 2026
Merged

fix: handle fractional device pixel ratio in Emscripten #168

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330e0c9
fix: handle fractional device pixel ratio in Emscripten canvas sizing
zfogg Feb 27, 2026
c65eae8
fix: correct DPR calculation in window.size() for fractional scaling
zfogg Feb 27, 2026
6cb3273
simplify: remove set_canvas_size_with_dpr, apply 1-line DPR fix to se…
claude Mar 18, 2026
35fe091
refactor: move DPR calculation to Nim side
zfogg Mar 18, 2026
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18 changes: 8 additions & 10 deletions src/windy/platforms/emscripten/platform.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -110,9 +110,10 @@ proc pollEvents*() =
emscripten_sleep(0)

proc size*(window: Window): IVec2 =
# Get the size of the canvas.
result.x = get_window_width() * get_device_pixel_ratio().int32
result.y = get_window_height() * get_device_pixel_ratio().int32
# Get the size of the canvas in physical pixels (CSS size × DPR).
let dpr = get_device_pixel_ratio()
result.x = (get_window_width().float32 * dpr).int32
result.y = (get_window_height().float32 * dpr).int32

proc `size=`*(window: Window, size: IVec2) =
## Size cannot be set on emscripten windows.
Expand Down Expand Up @@ -193,14 +194,11 @@ proc `focused=`*(window: Window, focused: bool) =
discard # Focus is controlled by browser

proc updateCanvasSize(window: Window) =
let
width = get_window_width().int32
height = get_window_height().int32
contentScale = get_device_pixel_ratio().float32
size = ivec2(width, height)
## Update canvas size to match window dimensions scaled by device pixel ratio.
let dpr = get_device_pixel_ratio()
set_canvas_size(
(size.x.float32 * contentScale).int32,
(size.y.float32 * contentScale).int32
(get_window_width().float32 * dpr).round().int32,
(get_window_height().float32 * dpr).round().int32
)

proc contentScale*(window: Window): float32 =
Expand Down
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