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feat(windows): a window sized by the display's scale, as a Retina Mac does

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A game asking for 960 x 540 got 960 x 540 pixels - a quarter of a 4K panel.
w_fit_scale turns the display's DPI into a whole-number scale (96 -> 1, 168 and
192 -> 2), brought down until the window fits; win_open and win_gl_resize size
the client area with it, win_gl_scale reports it the way cocoa.ll reports the
backing scale, and the mouse still arrives in the game's own units.

Verified on a 3840x2160 panel at 175%: windowed gl_triangle's 640x360 window
draws a 1280x720 frame.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Orkun ÇAKILKAYA 2026-09-13 02:46:00 +03:00
parent 3300fb3957
commit 63d9f61bf1
2 changed files with 79 additions and 15 deletions
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50
runtime/native/win32.ll
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@ -128,6 +128,43 @@ def:
ret i64 %r
}
declare i32 @GetDpiForSystem()
declare i32 @GetDpiForWindow(ptr)
; The display's scale as a whole number, the way macOS reports a backing scale: 96 dpi
; is 1, 175% (168 dpi) and 200% are 2, 300% is 3 - rounded, then brought down until a
; client area of w x h at that scale fits on the primary display. Shared with
; win32_gl.ll. A window of "960 x 540" is then the same size on the desk on a 4K
; panel as on a 1080p one, which is what a game asking for 960 x 540 means.
define i32 @w_fit_scale(i32 %dpi, i32 %w, i32 %h) {
entry:
%d0 = icmp slt i32 %dpi, 96
%d = select i1 %d0, i32 96, i32 %dpi
%d48 = add i32 %d, 48
%s0 = sdiv i32 %d48, 96
%sw = call i32 @GetSystemMetrics(i32 0)
%sh = call i32 @GetSystemMetrics(i32 1)
br label %fit
fit:
%s = phi i32 [ %s0, %entry ], [ %s1, %shrink ]
%one = icmp sle i32 %s, 1
br i1 %one, label %done, label %test
test:
%cw = mul i32 %w, %s
%ch = mul i32 %h, %s
%wide = icmp sgt i32 %cw, %sw
%tall = icmp sgt i32 %ch, %sh
%over = or i1 %wide, %tall
br i1 %over, label %shrink, label %done
shrink:
%s1 = sub i32 %s, 1
br label %fit
done:
%r0 = icmp slt i32 %s, 1
%r = select i1 %r0, i32 1, i32 %s
ret i32 %r
}
define void @win_open(i32 %w, i32 %h, i32 %scale, ptr %title) {
entry:
%wc = alloca [80 x i8], align 8
@ -142,6 +179,13 @@ entry:
make:
; DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 = -4
%dpi = call i32 @SetProcessDpiAwarenessContext(ptr inttoptr (i64 -4 to ptr))
; the framebuffer's own scale, times the display's
%sysdpi = call i32 @GetDpiForSystem()
%gw = mul i32 %w, %scale
%gh = mul i32 %h, %scale
%ds = call i32 @w_fit_scale(i32 %sysdpi, i32 %gw, i32 %gh)
%scale2 = mul i32 %scale, %ds
store i32 %scale2, ptr @W_scale
%inst = call ptr @GetModuleHandleA(ptr null)
; WNDCLASSEXA: cbSize 0, style 4, lpfnWndProc 8, hInstance 24, hCursor 40, lpszClassName 64
call void @llvm.memset.p0.i64(ptr %wc, i8 0, i64 80, i1 false)
@ -158,9 +202,9 @@ make:
%wcn = getelementptr i8, ptr %wc, i64 64
store ptr @.w_class, ptr %wcn
%atom = call i16 @RegisterClassExA(ptr %wc)
; the client area is w*scale x h*scale pixels; the frame goes round it
%pw = mul i32 %w, %scale
%ph = mul i32 %h, %scale
; the client area is w x h at both scales; the frame goes round it
%pw = mul i32 %gw, %ds
%ph = mul i32 %gh, %ds
call void @llvm.memset.p0.i64(ptr %rc, i8 0, i64 16, i1 false)
%rcr = getelementptr i8, ptr %rc, i64 8
store i32 %pw, ptr %rcr