From ebfab63ea702de08bd054febacadb2dea5dfb8a9 Mon Sep 17 00:00:00 2001
From: Jad Seifeddine <jad.seifeddine@icloud.com>
Date: Sun, 11 Oct 2026 04:11:10 +0700
Subject: [PATCH] client: fill a small framebuffer shortfall instead of leaving
 a strip

Windows RDP without GFX rounds the requested width down to a multiple
of 16, so a 1710-wide window gets a 1696-wide desktop. The uniform fit
in scaleDisplay() then keeps the scale at 1 (the height matches) and
the missing 14px shows as a strip of bare page down the right edge.

After the uniform fit, stretch the display element by the remaining
fraction on each axis when it is at most 2.5%, and divide the same
factors out of pointer coordinates before sendMouseState. A larger gap
is a real aspect mismatch and keeps the letterbox. Multi-monitor
pop-outs reset the fill.

Fixes #251
---
 static/client.html | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/static/client.html b/static/client.html
index d5f7166..37f2924 100644
--- a/static/client.html
+++ b/static/client.html
@@ -1859,12 +1859,46 @@
                 if (document.hidden) keyboard.reset();
             });
 
-            // Mouse input
+            // Mouse input. Pointer positions come in screen pixels of the
+            // display element; sendMouseState divides out the uniform display
+            // scale, and the fill factors from scaleDisplay() are divided out
+            // here, since they are a transform the display knows nothing about.
+            var fillX = 1, fillY = 1;
             var mouse = new Guacamole.Mouse(client.getDisplay().getElement());
             mouse.onEach(['mousedown', 'mousemove', 'mouseup'], function(e) {
-                client.sendMouseState(e.state, true);
+                var state = e.state;
+                if (fillX !== 1 || fillY !== 1) {
+                    state = new Guacamole.Mouse.State(state);
+                    state.x /= fillX;
+                    state.y /= fillY;
+                }
+                client.sendMouseState(state, true);
             });
 
+            // Absorb a small shortfall between the framebuffer and the
+            // viewport. The uniform fit in scaleDisplay() makes one axis match
+            // exactly and leaves the other short when the server could not
+            // honour the requested size: Windows RDP without GFX rounds the
+            // width down to a multiple of 16, so a 1710-wide window gets a
+            // 1696-wide desktop and a 14px strip of bare page down the right
+            // edge (#251). A stretch of that last percent or two is invisible;
+            // the strip is not. A larger gap is a real aspect mismatch (fixed
+            // resolution, no resize support) and keeps the letterbox.
+            var FILL_MAX = 1.025;
+            function applyFill(el, w, h, availW, availH) {
+                fillX = 1;
+                fillY = 1;
+                if (w > 0 && w < availW && availW / w <= FILL_MAX) fillX = availW / w;
+                if (h > 0 && h < availH && availH / h <= FILL_MAX) fillY = availH / h;
+                if (fillX !== 1 || fillY !== 1) {
+                    el.style.transformOrigin = '0 0';
+                    el.style.transform = 'scale(' + fillX + ', ' + fillY + ')';
+                } else {
+                    el.style.transformOrigin = '';
+                    el.style.transform = '';
+                }
+            }
+
             // Show the remote pointer image as the browser's own pointer, and
             // only fall back to the display's software cursor layer where CSS
             // cursors are unsupported. Guacamole.Display puts that layer in
@@ -1942,10 +1976,12 @@
                     // Monitor 0 is at combined (0,0); no negative offset needed.
                     el.style.marginLeft = '0';
                     el.style.marginTop = '0';
+                    applyFill(el, 0, 0, 0, 0);
                 }
                 else {
                     // Single display: scale the whole framebuffer to fit.
                     display.scale(Math.min(availW / dw, availH / dh));
+                    applyFill(el, dw * display.getScale(), dh * display.getScale(), availW, availH);
                     displayEl.style.overflow = '';
                     displayEl.style.position = '';
                     displayEl.style.width = '';