commit 39885eb71eb4eeaea45e3a1e7e0ead77e1ec2ec1
Author: Pierre Ossman <ossman@cendio.se>
Date:   Thu Nov 1 10:19:15 2018 +0100

    Maintain static screen DPI on resize
    
    Trying to dynamically track the DPI did not really work as we'd
    start accumulating errors and eventually the DPI would start to
    drift. Instead maintain a fixed, sensible DPI at all times.

diff --git a/unix/x0vncserver/RandrGlue.c b/unix/x0vncserver/RandrGlue.c
index ff12902f..c26ac6ad 100644
--- a/unix/x0vncserver/RandrGlue.c
+++ b/unix/x0vncserver/RandrGlue.c
@@ -117,15 +117,15 @@ int vncRandRResizeScreen(int width, int height)
 {
   vncGlueContext *ctx = &randrGlueContext;
 
-  int xwidth = DisplayWidth(ctx->dpy, DefaultScreen(ctx->dpy));
-  int xheight = DisplayHeight(ctx->dpy, DefaultScreen(ctx->dpy));
-  int xwidthmm = DisplayWidthMM(ctx->dpy, DefaultScreen(ctx->dpy));
-  int xheightmm = DisplayHeightMM(ctx->dpy, DefaultScreen(ctx->dpy));
+  int mwidth, mheight;
 
-  /* Try to retain DPI when we resize */
-  XRRSetScreenSize(ctx->dpy, DefaultRootWindow(ctx->dpy), width, height,
-                   xwidthmm * width / xwidth,
-                   xheightmm * height / xheight);
+  // Always calculate a DPI of 96.
+  // It's what mutter does, so good enough for us.
+  mwidth = width * 254 / 96 / 10;
+  mheight = height * 254 / 96 / 10;
+
+  XRRSetScreenSize(ctx->dpy, DefaultRootWindow(ctx->dpy),
+                   width, height, mwidth, mheight);
 
   return 1;
 }
diff --git a/unix/xserver/hw/vnc/RandrGlue.c b/unix/xserver/hw/vnc/RandrGlue.c
index 82e85524..a2916888 100644
--- a/unix/xserver/hw/vnc/RandrGlue.c
+++ b/unix/xserver/hw/vnc/RandrGlue.c
@@ -64,11 +64,14 @@ int vncRandRIsValidScreenSize(int width, int height)
 int vncRandRResizeScreen(int width, int height)
 {
   ScreenPtr pScreen = screenInfo.screens[scrIdx];
+  int dpi, mwidth, mheight;
 
-  /* Try to retain DPI when we resize */
-  return RRScreenSizeSet(pScreen, width, height,
-                         pScreen->mmWidth * width / pScreen->width,
-                         pScreen->mmHeight * height / pScreen->height);
+  /* Keep the DPI specified at start */
+  dpi = monitorResolution ? monitorResolution : 96;
+  mwidth = width * 254 / dpi / 10;
+  mheight = height * 254 / dpi / 10;
+
+  return RRScreenSizeSet(pScreen, width, height, mwidth, mheight);
 }
 
 void vncRandRUpdateSetTime(void)