extract cell-pixel geometry from linux framebuffer console #1369

src/lib/linux.c

@@ -417,22 +417,33 @@ bool is_linux_console(int fd, unsigned no_font_changes, bool* quadrants){
   return true;
 }
 
+int get_linux_fb_pixelgeom(int fd, unsigned* ypix, unsigned *xpix){
+  struct fb_var_screeninfo fbi = {};
+  if(ioctl(fd, FBIOGET_VSCREENINFO, &fbi)){
+    logwarn("Couldn't get framebuffer info from %d (%s?)\n", fd, strerror(errno));
+    return -1;
+  }
+  loginfo("Linux framebuffer geometry: %dx%d\n", fbi.yres, fbi.xres);
+  *ypix = fbi.yres;
+  *xpix = fbi.xres;
+  return 0;
+}
+
 bool is_linux_framebuffer(tinfo* ti){
   // FIXME there might be multiple framebuffers present; how do we determine
   // which one is ours?
   const char* dev = "/dev/fb0";
+  loginfo("Checking for Linux framebuffer at %s\n", dev);
   int fd = open(dev, O_RDWR | O_CLOEXEC);
   if(fd < 0){
     logdebug("Couldn't open framebuffer device %s\n", dev);
     return false;
   }
-  struct fb_var_screeninfo fbi = {};
-  if(ioctl(fd, FBIOGET_VSCREENINFO, &fbi)){
-    logdebug("Couldn't get framebuffer info from %s (%s?)\n", dev, strerror(errno));
+  unsigned y, x;
+  if(get_linux_fb_pixelgeom(fd, &y, &x)){
     close(fd);
     return false;
   }
-  loginfo("Linux framebuffer detected at %s: %dx%d\n", dev, fbi.yres, fbi.xres);
   ti->linux_fb_fd = fd;
   return true;
 }
@@ -448,4 +459,11 @@ bool is_linux_framebuffer(tinfo* ti){
   (void)ti;
   return false;
 }
+
+int get_linux_fb_pixelgeom(int fd, unsigned* ypix, unsigned *xpix){
+  (void)fd;
+  (void)ypix;
+  (void)xpix;
+  return -1;
+}
 #endif

src/lib/linux.h

@@ -11,10 +11,14 @@ struct tinfo;
 
 bool is_linux_console(int fd, unsigned no_font_changes, bool* quadrants);
 
-// if is_linux_console returned true, call this to determine whether it is
-// a drawable framebuffer console. do not call if not is_linux_console!
+// if is_linux_console() returned true, call this to determine whether it is
+// a drawable framebuffer console. do not call if not a verified console!
 bool is_linux_framebuffer(struct tinfo* ti);
 
+// call only on an fd where is_linux_framebuffer() returned true. gets the
+// pixel geometry for the visual area.
+int get_linux_fb_pixelgeom(int fd, unsigned* ypix, unsigned *xpix);
+
 #ifdef __cplusplus
 }
 #endif

src/lib/notcurses.c

@@ -1,4 +1,5 @@
 #include "input.h"
+#include "linux.h"
 #include "version.h"
 #include "egcpool.h"
 #include "internal.h"
@@ -247,8 +248,15 @@ int update_term_dimensions(int fd, int* rows, int* cols, tinfo* tcache,
     *cols = ws.ws_col;
   }
   if(tcache){
-    tcache->cellpixy = ws.ws_row ? ws.ws_ypixel / ws.ws_row : 0;
-    tcache->cellpixx = ws.ws_col ? ws.ws_xpixel / ws.ws_col : 0;
+    unsigned y, x;
+    if(tcache->linux_fb_fd >= 0){
+      get_linux_fb_pixelgeom(tcache->linux_fb_fd, &y, &x);
+    }else{
+      y = ws.ws_ypixel;
+      x = ws.ws_xpixel;
+    }
+    tcache->cellpixy = ws.ws_row ? y / ws.ws_row : 0;
+    tcache->cellpixx = ws.ws_col ? x / ws.ws_col : 0;
     if(tcache->cellpixy == 0 || tcache->cellpixx == 0){
       tcache->pixel_draw = NULL; // disable support
     }