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Return xrandr-scaled display modes 

XRandR supports applying transformations to an output's picture
including changes to scale. Such scaling is used by some desktop
environments under feature names such as "fractional scaling" to
accomodate HiDPI devices. Alternatively, such scaling can be enabled by
a command such as the following:

xrandr --output DP1 --scale 0.5x0.5 --filter nearest

XRandR scaling has no "HiDPI awareness" or other way for an application
to signal that it wants to work with physical display pixels, and so all
we do is scale SDL's returned display modes so that applications receive
the number of usable pixels that they expect.
main
Jeffrey Knockel 2022-03-20 18:52:49 -04:00 committed by Sam Lantinga
parent 4d6ed7173e
commit e4eab186ec
2 changed files with 12 additions and 4 deletions
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15
src/video/x11/SDL_x11modes.c
View File

@ -397,19 +397,26 @@ static SDL_bool SetXRandRModeInfo(Display *display, XRRScreenResources *res, RRC
if (info->id == modeID) {
XRRCrtcInfo *crtcinfo;
Rotation rotation = 0;
XFixed scale_w = 0x10000, scale_h = 0x10000;
XRRCrtcTransformAttributes *attr;
crtcinfo = X11_XRRGetCrtcInfo(display, res, crtc);
if (crtcinfo) {
rotation = crtcinfo->rotation;
X11_XRRFreeCrtcInfo(crtcinfo);
}
if (X11_XRRGetCrtcTransform(display, crtc, &attr) && attr) {
scale_w = attr->currentTransform.matrix[0][0];
scale_h = attr->currentTransform.matrix[1][1];
X11_XFree(attr);
}
if (rotation & (XRANDR_ROTATION_LEFT | XRANDR_ROTATION_RIGHT)) {
mode->w = info->height;
mode->h = info->width;
mode->w = (info->height * scale_w + 0xffff) >> 16;
mode->h = (info->width * scale_h + 0xffff) >> 16;
} else {
mode->w = info->width;
mode->h = info->height;
mode->w = (info->width * scale_w + 0xffff) >> 16;
mode->h = (info->height * scale_h + 0xffff) >> 16;
}
mode->refresh_rate = CalculateXRandRRefreshRate(info);
((SDL_DisplayModeData *)mode->driverdata)->xrandr_mode = modeID;

1
src/video/x11/SDL_x11sym.h
View File

@ -309,6 +309,7 @@ SDL_X11_SYM(XRRPropertyInfo*,XRRQueryOutputProperty,(Display *dpy,RROutput outpu
SDL_X11_SYM(int,XRRGetOutputProperty,(Display *dpy,RROutput output, Atom property, long offset, long length, Bool _delete, Bool pending, Atom req_type, Atom *actual_type, int *actual_format, unsigned long *nitems, unsigned long *bytes_after, unsigned char **prop),(dpy,output,property,offset,length, _delete, pending, req_type, actual_type, actual_format, nitems, bytes_after, prop),return)
SDL_X11_SYM(RROutput,XRRGetOutputPrimary,(Display *dpy,Window window),(dpy,window),return)
SDL_X11_SYM(void,XRRSelectInput,(Display *dpy, Window window, int mask),(dpy,window,mask),)
SDL_X11_SYM(Status,XRRGetCrtcTransform,(Display *dpy,RRCrtc crtc,XRRCrtcTransformAttributes **attributes),(dpy,crtc,attributes),return)
#endif
/* MIT-SCREEN-SAVER support */