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changeset 27181:5754e8d8199a

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guess screen dpi if screen size is reported to be zero * cdisplay.c (octave_get_display_info): Guess screen DPI if screen size is zero. Refactor to perform DPI calculation and error detection in one place.
author John W. Eaton <jwe@octave.org>
date Thu, 13 Jun 2019 09:23:11 -0500
parents 269d71efaf04
children 0beeb6817376
files libinterp/corefcn/cdisplay.c
diffstat 1 files changed, 30 insertions(+), 15 deletions(-) [+]
line wrap: on
line diff
--- a/libinterp/corefcn/cdisplay.c	Wed Jun 12 16:55:22 2019 -0500
+++ b/libinterp/corefcn/cdisplay.c	Thu Jun 13 09:23:11 2019 -0500
@@ -55,6 +55,9 @@
 
   *dpy_avail = 0;
 
+  double ht_mm = 0.0;
+  double wd_mm = 0.0;
+
 #if defined (OCTAVE_USE_WINDOWS_API)
 
   octave_unused_parameter (dpy_name);
@@ -68,11 +71,8 @@
       *ht = GetDeviceCaps (hdc, VERTRES);
       *wd = GetDeviceCaps (hdc, HORZRES);
 
-      double ht_mm = GetDeviceCaps (hdc, VERTSIZE);
-      double wd_mm = GetDeviceCaps (hdc, HORZSIZE);
-
-      *rx = *wd * 25.4 / wd_mm;
-      *ry = *ht * 25.4 / ht_mm;
+      ht_mm = GetDeviceCaps (hdc, VERTSIZE);
+      wd_mm = GetDeviceCaps (hdc, HORZSIZE);
 
       *dpy_avail = 1;
     }
@@ -118,11 +118,8 @@
          values, but the CGFloat typedef is not present on older
          systems, so use double instead.  */
 
-      double ht_mm = sz_mm.height;
-      double wd_mm = sz_mm.width;
-
-      *rx = *wd * 25.4 / wd_mm;
-      *ry = *ht * 25.4 / ht_mm;
+      ht_mm = sz_mm.height;
+      wd_mm = sz_mm.width;
 
       *dpy_avail = 1;
     }
@@ -149,11 +146,8 @@
 
           int screen_number = XScreenNumberOfScreen (screen);
 
-          double ht_mm = DisplayHeightMM (display, screen_number);
-          double wd_mm = DisplayWidthMM (display, screen_number);
-
-          *rx = *wd * 25.4 / wd_mm;
-          *ry = *ht * 25.4 / ht_mm;
+          ht_mm = DisplayHeightMM (display, screen_number);
+          wd_mm = DisplayWidthMM (display, screen_number);
         }
       else
         msg = "X11 display has no default screen";
@@ -178,5 +172,26 @@
 
 #endif
 
+  if (*dpy_avail)
+    {
+      if (wd_mm == 0 || ht_mm == 0)
+        {
+          msg = "screen width or height reported to be zero";
+
+          // Sizes reported as zero have been found on some systems.
+          // For example, X/Wayland running inside virtualbox.
+
+          // Guess a DPI.
+
+          *rx = 96.0;
+          *ry = 96.0;
+        }
+      else
+        {
+          *rx = *wd * 25.4 / wd_mm;
+          *ry = *ht * 25.4 / ht_mm;
+        }
+    }
+
   return msg;
 }