Commit c289bad9007cb672c994f726d967f6e5682f200d
2021-03-22T11:22:31
In x11, GetDisplayDPI can give incorrect or unusable DPI information. Using XGetDefaults to get the Xft DPI if it's available and returning that. This could allow you to figure out DPI scale.
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diff --git a/src/video/x11/SDL_x11modes.c b/src/video/x11/SDL_x11modes.c
index f35e34b..3e1d456 100644
--- a/src/video/x11/SDL_x11modes.c
+++ b/src/video/x11/SDL_x11modes.c
@@ -345,6 +345,29 @@ SetXRandRDisplayName(Display *dpy, Atom EDID, char *name, const size_t namelen,
#endif
}
+static int
+GetXftDPI(Display* dpy)
+{
+ char* xdefault_resource;
+ int xft_dpi, err;
+
+ xdefault_resource = X11_XGetDefault(dpy, "Xft", "dpi");
+
+ if(!xdefault_resource) {
+ return 0;
+ }
+
+ /*
+ * It's possible for SDL_atoi to call strtol, if it fails due to a
+ * overflow or an underflow, it will return LONG_MAX or LONG_MIN and set
+ * errno to ERANGE. So we need to check for this so we dont get crazy dpi
+ * values
+ */
+ xft_dpi = SDL_atoi(xdefault_resource);
+ err = errno;
+
+ return err == ERANGE ? 0 : xft_dpi;
+}
static int
X11_InitModes_XRandR(_THIS)
@@ -417,6 +440,7 @@ X11_InitModes_XRandR(_THIS)
RRMode modeID;
RRCrtc output_crtc;
XRRCrtcInfo *crtc;
+ float xft_dpi;
/* The primary output _should_ always be sorted first, but just in case... */
if ((looking_for_primary && (res->outputs[output] != primary)) ||
@@ -471,6 +495,14 @@ X11_InitModes_XRandR(_THIS)
displaydata->hdpi = display_mm_width ? (((float) mode.w) * 25.4f / display_mm_width) : 0.0f;
displaydata->vdpi = display_mm_height ? (((float) mode.h) * 25.4f / display_mm_height) : 0.0f;
displaydata->ddpi = SDL_ComputeDiagonalDPI(mode.w, mode.h, ((float) display_mm_width) / 25.4f,((float) display_mm_height) / 25.4f);
+
+ /* if xft dpi is available we will use this over xrandr */
+ xft_dpi = (float)GetXftDPI(dpy);
+ if(xft_dpi > 0) {
+ displaydata->hdpi = xft_dpi;
+ displaydata->vdpi = xft_dpi;
+ }
+
displaydata->scanline_pad = scanline_pad;
displaydata->x = display_x;
displaydata->y = display_y;
diff --git a/src/video/x11/SDL_x11sym.h b/src/video/x11/SDL_x11sym.h
index b6e3a87..6433b93 100644
--- a/src/video/x11/SDL_x11sym.h
+++ b/src/video/x11/SDL_x11sym.h
@@ -138,6 +138,7 @@ SDL_X11_SYM(int,XWarpPointer,(Display* a,Window b,Window c,int d,int e,unsigned
SDL_X11_SYM(int,XWindowEvent,(Display* a,Window b,long c,XEvent* d),(a,b,c,d),return)
SDL_X11_SYM(Status,XWithdrawWindow,(Display* a,Window b,int c),(a,b,c),return)
SDL_X11_SYM(VisualID,XVisualIDFromVisual,(Visual* a),(a),return)
+SDL_X11_SYM(char*,XGetDefault,(Display* a,char* b, char* c),(a,b,c),return)
#if SDL_VIDEO_DRIVER_X11_CONST_PARAM_XEXTADDDISPLAY
SDL_X11_SYM(XExtDisplayInfo*,XextAddDisplay,(XExtensionInfo* a,Display* b,_Xconst char* c,XExtensionHooks* d,int e,XPointer f),(a,b,c,d,e,f),return)
#else