Add fractional scales to auto scale guessing

1 files changed, 18 insertions, 20 deletions

diff --git a/src/utils/scale.rs b/src/utils/scale.rs
index 6db88248..857b3825 100644
--- a/src/utils/scale.rs
+++ b/src/utils/scale.rs
@@ -7,6 +7,7 @@ use smithay::utils::{Physical, Raw, Size};
 
 const MIN_SCALE: i32 = 1;
 const MAX_SCALE: i32 = 4;
+const STEPS: i32 = 4;
 const MIN_LOGICAL_AREA: i32 = 800 * 480;
 
 const MOBILE_TARGET_DPI: f64 = 135.;
@@ -31,9 +32,6 @@ pub fn guess_monitor_scale(size_mm: Size<i32, Raw>, resolution: Size<i32, Physic
         f64::from(resolution.w * resolution.w + resolution.h * resolution.h).sqrt() / diag_inches;
     let perfect_scale = physical_dpi / target_dpi;
 
-    // For integer scaling factors (we currently only do integer), bias the perfect scale down.
-    let perfect_scale = perfect_scale - 0.15;
-
     supported_scales(resolution)
         .map(|scale| (scale, (scale - perfect_scale).abs()))
         .min_by(|a, b| a.1.partial_cmp(&b.1).unwrap())
@@ -41,13 +39,13 @@ pub fn guess_monitor_scale(size_mm: Size<i32, Raw>, resolution: Size<i32, Physic
 }
 
 fn supported_scales(resolution: Size<i32, Physical>) -> impl Iterator<Item = f64> {
-    (MIN_SCALE..=MAX_SCALE)
+    (MIN_SCALE * STEPS..=MAX_SCALE * STEPS)
+        .map(|x| f64::from(x) / f64::from(STEPS))
         .filter(move |scale| is_valid_for_resolution(resolution, *scale))
-        .map(f64::from)
 }
 
-fn is_valid_for_resolution(resolution: Size<i32, Physical>, scale: i32) -> bool {
-    let logical = resolution.to_logical(scale);
+fn is_valid_for_resolution(resolution: Size<i32, Physical>, scale: f64) -> bool {
+    let logical = resolution.to_f64().to_logical(scale).to_i32_round::<i32>();
     logical.w * logical.h >= MIN_LOGICAL_AREA
 }
 
@@ -71,33 +69,33 @@ mod tests {
     #[test]
     fn test_guess_monitor_scale() {
         // Librem 5; not enough logical area when scaled
-        snapshot!(check((65, 129), (720, 1440)), "1.0");
+        snapshot!(check((65, 129), (720, 1440)), "1.5");
         // OnePlus 6
-        snapshot!(check((68, 144), (1080, 2280)), "2.0");
+        snapshot!(check((68, 144), (1080, 2280)), "2.5");
         // Google Pixel 6a
-        snapshot!(check((64, 142), (1080, 2400)), "2.0");
+        snapshot!(check((64, 142), (1080, 2400)), "2.5");
         // 13" MacBook Retina
-        snapshot!(check((286, 179), (2560, 1600)), "2.0");
+        snapshot!(check((286, 179), (2560, 1600)), "1.75");
         // Surface Laptop Studio
-        snapshot!(check((303, 202), (2400, 1600)), "1.0");
+        snapshot!(check((303, 202), (2400, 1600)), "1.5");
         // Dell XPS 9320
-        snapshot!(check((290, 180), (3840, 2400)), "2.0");
+        snapshot!(check((290, 180), (3840, 2400)), "2.5");
         // Lenovo ThinkPad X1 Yoga Gen 6
-        snapshot!(check((300, 190), (3840, 2400)), "2.0");
+        snapshot!(check((300, 190), (3840, 2400)), "2.5");
         // Generic 23" 1080p
         snapshot!(check((509, 286), (1920, 1080)), "1.0");
         // Generic 23" 4K
-        snapshot!(check((509, 286), (3840, 2160)), "2.0");
+        snapshot!(check((509, 286), (3840, 2160)), "1.75");
         // Generic 27" 4K
-        snapshot!(check((598, 336), (3840, 2160)), "1.0");
+        snapshot!(check((598, 336), (3840, 2160)), "1.5");
         // Generic 32" 4K
-        snapshot!(check((708, 398), (3840, 2160)), "1.0");
+        snapshot!(check((708, 398), (3840, 2160)), "1.25");
         // Generic 25" 4K; ideal scale is 1.60, should round to 1.5 and 1.0
-        snapshot!(check((554, 312), (3840, 2160)), "1.0");
+        snapshot!(check((554, 312), (3840, 2160)), "1.5");
         // Generic 23.5" 4K; ideal scale is 1.70, should round to 1.75 and 2.0
-        snapshot!(check((522, 294), (3840, 2160)), "2.0");
+        snapshot!(check((522, 294), (3840, 2160)), "1.75");
         // Lenovo Legion 7 Gen 7 AMD 16"
-        snapshot!(check((340, 210), (2560, 1600)), "1.0");
+        snapshot!(check((340, 210), (2560, 1600)), "1.5");
         // Acer Nitro XV320QU LV 31.5"
         snapshot!(check((700, 390), (2560, 1440)), "1.0");
         // Surface Pro 6