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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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44
runtime/native/win32_gl.ll
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@ -6,11 +6,16 @@
; entry-point table). A headless build links gl_win_nowin.ll in its place.
;
; win_gl_attach() -> ok the context on the window's DC (0 = no window yet)
; win_gl_resize(w, h) client area of w x h pixels, centred
; win_gl_resize(w, h) a client area of w x h at the display's scale, centred
; win_gl_swap() SwapBuffers, paced by the swap interval
; win_gl_scale() -> 1 the process is DPI aware: one pixel is one pixel
; win_gl_scale() -> int pixels per window unit: 1 at 100%, 2 at 175-200%, ...
; win_gl_drawable(out) the client area in pixels
; win_toggle_fullscreen() borderless, over the monitor the window is on
;
; The units follow cocoa.ll's points and backing pixels: a game asks for a 960 x 540
; window, the display's whole-number scale (w_fit_scale, win32.ll) turns that into
; pixels, win_gl_scale reports the factor as the Retina backing scale is reported,
; and the mouse keeps arriving in the game's own units because W_scale divides by it.
; ============================================================================
@W_hwnd = external global ptr
@ -19,6 +24,7 @@
@W_fbh = external global i32
@W_scale = external global i32
declare i32 @w_fit_scale(i32, i32, i32)
declare ptr @lgl_wgl_core(ptr, i32)
declare ptr @wglGetProcAddress(ptr)
declare i32 @SwapBuffers(ptr)
@ -26,6 +32,7 @@ declare i32 @GetClientRect(ptr, ptr)
declare i32 @AdjustWindowRectEx(ptr, i32, i32, i32)
declare i32 @SetWindowPos(ptr, ptr, i32, i32, i32, i32, i32)
declare i32 @GetSystemMetrics(i32)
declare i32 @GetDpiForWindow(ptr)
declare i64 @GetWindowLongPtrA(ptr, i32)
declare i64 @SetWindowLongPtrA(ptr, i32, i64)
declare i32 @GetWindowRect(ptr, ptr)
@ -36,6 +43,7 @@ declare void @llvm.memset.p0.i64(ptr, i8, i64, i1)
@.wgl_swapint = private unnamed_addr constant [19 x i8] c"wglSwapIntervalEXT\00"
@W_glctx = internal global ptr null
@W_glscale = internal global i32 1
@W_fs = internal global i32 0
@W_fs_style = internal global i64 0
@W_fs_rect = internal global [4 x i32] zeroinitializer
@ -71,18 +79,23 @@ entry:
%nowin = icmp eq ptr %hwnd, null
br i1 %nowin, label %out, label %go
go:
%dpi = call i32 @GetDpiForWindow(ptr %hwnd)
%s = call i32 @w_fit_scale(i32 %dpi, i32 %w, i32 %h)
store i32 %s, ptr @W_glscale
store i32 %w, ptr @W_fbw
store i32 %h, ptr @W_fbh
store i32 1, ptr @W_scale
store i32 %s, ptr @W_scale
%fs = load i32, ptr @W_fs
%isfs = icmp ne i32 %fs, 0
br i1 %isfs, label %out, label %size
size:
%pw = mul i32 %w, %s
%ph = mul i32 %h, %s
call void @llvm.memset.p0.i64(ptr %rc, i8 0, i64 16, i1 false)
%rcr = getelementptr i8, ptr %rc, i64 8
store i32 %w, ptr %rcr
store i32 %pw, ptr %rcr
%rcb = getelementptr i8, ptr %rc, i64 12
store i32 %h, ptr %rcb
store i32 %ph, ptr %rcb
%style64 = call i64 @GetWindowLongPtrA(ptr %hwnd, i32 -16) ; GWL_STYLE
%style = trunc i64 %style64 to i32
%adj = call i32 @AdjustWindowRectEx(ptr %rc, i32 %style, i32 0, i32 0)
@ -124,7 +137,8 @@ out:
define i32 @win_gl_scale() {
entry:
ret i32 1
%s = load i32, ptr @W_glscale
ret i32 %s
}
; 1 = vsync (set at attach), 0 = free-running; wglSwapIntervalEXT is a driver extension,
@ -147,6 +161,8 @@ out:
ret void
}
; the client area in pixels -> out[0], out[1]; and the window size in the game's units,
; which the mouse mapping divides by, kept in step with a window the player resized
define void @win_gl_drawable(ptr %out) {
entry:
%rc = alloca [16 x i8], align 4
@ -162,14 +178,18 @@ go:
store i32 %w, ptr %out
%o1 = getelementptr i32, ptr %out, i32 1
store i32 %h, ptr %o1
; a minimised window has no client area; keep the last real size for the mouse mapping
; a minimised window has no client area; keep the last real size
%zw = icmp sle i32 %w, 0
%zh = icmp sle i32 %h, 0
%gone = or i1 %zw, %zh
br i1 %gone, label %done, label %track
track:
store i32 %w, ptr @W_fbw
store i32 %h, ptr @W_fbh
%s = load i32, ptr @W_glscale
%uw = sdiv i32 %w, %s
%uh = sdiv i32 %h, %s
store i32 %uw, ptr @W_fbw
store i32 %uh, ptr @W_fbh
store i32 %s, ptr @W_scale
br label %done
done:
ret void
@ -186,9 +206,9 @@ entry:
ret void
}
; The Retina switch: on Windows the process is DPI aware and always draws one pixel per
; screen pixel, which is what "on" means on macOS; there is no lower-resolution surface
; for "off" to fall back to, so it changes nothing.
; The Retina switch. The process is DPI aware and always draws one pixel per screen
; pixel, which is what "on" means on macOS; there is no lower-resolution surface for
; "off" to fall back to, so it changes nothing here.
define void @win_gl_retina(i32 %on) {
entry:
ret void