Handle fractional screen sizes

With high DPI systems we can end up with a container with a size that
is not an integer number of CSS pixels. Make sure we can handle those
cases by allowing a fractional size for the output canvas. Framebuffer
size and viewport coordinates are still restricted to integer dimensions
though.

Based on initial patch by Alexander E. Patrakov.

2 files changed, 9 insertions, 5 deletions

diff --git a/core/display.js b/core/display.js
index 4955ce2..d6db075 100644
--- a/core/display.js
+++ b/core/display.js
@@ -168,6 +168,9 @@ export default class Display {
             height = this._fb_height;
         }
 
+        width = Math.floor(width);
+        height = Math.floor(height);
+
         if (width > this._fb_width) {
             width = this._fb_width;
         }
@@ -524,8 +527,8 @@ export default class Display {
         //                   style width to a number, the canvas is cleared.
         //                   However, if you set the style width to a string
         //                   ('NNNpx'), the canvas is scaled without clearing.
-        const width = Math.round(factor * vp.w) + 'px';
-        const height = Math.round(factor * vp.h) + 'px';
+        const width = factor * vp.w + 'px';
+        const height = factor * vp.h + 'px';
 
         if ((this._target.style.width !== width) ||
             (this._target.style.height !== height)) {
diff --git a/core/rfb.js b/core/rfb.js
index 3433030..f09e241 100644
--- a/core/rfb.js
+++ b/core/rfb.js
@@ -546,7 +546,8 @@ export default class RFB extends EventTargetMixin {
         }
 
         const size = this._screenSize();
-        RFB.messages.setDesktopSize(this._sock, size.w, size.h,
+        RFB.messages.setDesktopSize(this._sock,
+                                    Math.floor(size.w), Math.floor(size.h),
                                     this._screen_id, this._screen_flags);
 
         Log.Debug('Requested new desktop size: ' +
@@ -555,8 +556,8 @@ export default class RFB extends EventTargetMixin {
 
     // Gets the the size of the available screen
     _screenSize() {
-        return { w: this._screen.offsetWidth,
-                 h: this._screen.offsetHeight };
+        let r = this._screen.getBoundingClientRect();
+        return { w: r.width, h: r.height };
     }
 
     _fixScrollbars() {