fix: ceil integer scale for better text rendering on fractional scaling

crates/adapters/src/rendering/femtovg/renderable_window.rs

@@ -10,6 +10,46 @@ pub enum RenderState {
     Dirty,
 }
 
+#[derive(Debug, Clone, Copy)]
+pub struct FractionalScaleConfig {
+    pub render_scale: f32,
+    pub render_physical_size: PhysicalSize,
+    pub logical_width: f32,
+    pub logical_height: f32,
+}
+
+impl FractionalScaleConfig {
+    #[allow(clippy::cast_possible_truncation)]
+    #[allow(clippy::cast_sign_loss)]
+    #[must_use]
+    pub fn new(logical_width: f32, logical_height: f32, scale_factor: f32) -> Self {
+        let render_scale = Self::render_scale(scale_factor);
+        Self {
+            render_scale,
+            render_physical_size: PhysicalSize::new(
+                (logical_width * render_scale) as u32,
+                (logical_height * render_scale) as u32,
+            ),
+            logical_width,
+            logical_height,
+        }
+    }
+
+    #[must_use]
+    pub fn render_scale(scale_factor: f32) -> f32 {
+        scale_factor.ceil()
+    }
+
+    pub fn apply_to<W: RenderableWindow + ?Sized>(&self, window: &W) {
+        window.set_scale_factor(self.render_scale);
+        window.set_size_with_exact_logical(
+            self.render_physical_size,
+            self.logical_width,
+            self.logical_height,
+        );
+    }
+}
+
 pub trait RenderableWindow: WindowAdapter {
     fn render_frame_if_dirty(&self) -> Result<()>;
     fn set_scale_factor(&self, scale_factor: f32);
@@ -31,4 +71,16 @@ pub trait RenderableWindow: WindowAdapter {
             size: size.to_logical(self.scale_factor()),
         });
     }
+
+    fn set_size_with_exact_logical(
+        &self,
+        physical: slint::PhysicalSize,
+        logical_width: f32,
+        logical_height: f32,
+    ) {
+        self.size_cell().set(physical);
+        self.window().dispatch_event(WindowEvent::Resized {
+            size: slint::LogicalSize::new(logical_width, logical_height),
+        });
+    }
 }

crates/adapters/src/wayland/session_lock/manager/state.rs

@@ -1,7 +1,7 @@
 use super::callbacks::{LockCallbackContext, LockCallbackExt, LockPropertyOperationExt};
 use crate::errors::Result;
 use crate::rendering::femtovg::main_window::FemtoVGWindow;
-use crate::rendering::femtovg::renderable_window::RenderableWindow;
+use crate::rendering::femtovg::renderable_window::{FractionalScaleConfig, RenderableWindow};
 use crate::rendering::slint_integration::platform::CustomSlintPlatform;
 use crate::wayland::session_lock::lock_surface::LockSurface;
 use crate::wayland::surfaces::component_state::ComponentState;
@@ -308,7 +308,22 @@ impl ActiveLockSurface {
         scale_factor: f32,
     ) {
         match mode {
-            LockScalingMode::FractionalWithViewport | LockScalingMode::FractionalOnly => {
+            LockScalingMode::FractionalWithViewport => {
+                let config = FractionalScaleConfig::new(
+                    dimensions.logical_width() as f32,
+                    dimensions.logical_height() as f32,
+                    scale_factor,
+                );
+                info!(
+                    "Lock FractionalWithViewport: render scale {} (from {}), physical {}x{}",
+                    config.render_scale,
+                    scale_factor,
+                    config.render_physical_size.width,
+                    config.render_physical_size.height
+                );
+                config.apply_to(self.window.as_ref());
+            }
+            LockScalingMode::FractionalOnly => {
                 RenderableWindow::set_scale_factor(self.window.as_ref(), scale_factor);
                 self.window.set_size(WindowSize::Logical(LogicalSize::new(
                     dimensions.logical_width() as f32,

crates/adapters/src/wayland/surfaces/popup_manager.rs

@@ -1,6 +1,7 @@
 use crate::errors::{LayerShikaError, Result};
 use crate::rendering::egl::context_factory::RenderContextFactory;
-use crate::rendering::femtovg::{popup_window::PopupWindow, renderable_window::RenderableWindow};
+use crate::rendering::femtovg::popup_window::PopupWindow;
+use crate::rendering::femtovg::renderable_window::{FractionalScaleConfig, RenderableWindow};
 use crate::wayland::surfaces::display_metrics::{DisplayMetrics, SharedDisplayMetrics};
 use layer_shika_domain::dimensions::LogicalSize as DomainLogicalSize;
 use layer_shika_domain::surface_dimensions::SurfaceDimensions;
@@ -9,7 +10,7 @@ use layer_shika_domain::value_objects::popup_behavior::ConstraintAdjustment;
 use layer_shika_domain::value_objects::popup_config::PopupConfig;
 use layer_shika_domain::value_objects::popup_position::PopupPosition;
 use log::info;
-use slint::{platform::femtovg_renderer::FemtoVGRenderer, PhysicalSize, WindowSize};
+use slint::{platform::femtovg_renderer::FemtoVGRenderer, PhysicalSize};
 use smithay_client_toolkit::reexports::protocols_wlr::layer_shell::v1::client::zwlr_layer_surface_v1::ZwlrLayerSurfaceV1;
 use std::cell::{Cell, RefCell};
 use std::collections::{HashMap, VecDeque};
@@ -200,8 +201,9 @@ impl PopupManager {
     pub fn update_scale_factor(&self, scale_factor: f32) {
         self.scale_factor.set(scale_factor);
 
+        let render_scale = FractionalScaleConfig::render_scale(scale_factor);
         for popup in self.state.borrow().popups.values() {
-            popup.window.set_scale_factor(scale_factor);
+            popup.window.set_scale_factor(render_scale);
         }
         self.mark_all_popups_dirty();
     }
@@ -322,11 +324,16 @@ impl PopupManager {
 
         let popup_window = PopupWindow::new_with_callback(renderer, on_close);
         popup_window.set_popup_id(popup_id.to_handle());
-        popup_window.set_scale_factor(scale_factor);
-        popup_window.set_size(WindowSize::Logical(slint::LogicalSize::new(
-            params.width,
-            params.height,
-        )));
+
+        let config = FractionalScaleConfig::new(params.width, params.height, scale_factor);
+        info!(
+            "Popup using render scale {} (from {}), render_physical {}x{}",
+            config.render_scale,
+            scale_factor,
+            config.render_physical_size.width,
+            config.render_physical_size.height
+        );
+        config.apply_to(popup_window.as_ref());
 
         let mut state = self.state.borrow_mut();
         state.popups.insert(
@@ -489,7 +496,6 @@ impl PopupManager {
         ActiveWindow::None
     }
 
-    #[allow(clippy::cast_precision_loss)]
     pub fn update_scale_for_fractional_scale_object(
         &self,
         fractional_scale_proxy: &WpFractionalScaleV1,
@@ -500,8 +506,12 @@ impl PopupManager {
         if let Some(popup_key) = self.find_popup_key_by_fractional_scale_id(&fractional_scale_id) {
             if let Some(popup_surface) = self.get_popup_window(popup_key) {
                 let new_scale_factor = DisplayMetrics::scale_factor_from_120ths(scale_120ths);
-                info!("Updating popup scale factor to {new_scale_factor} ({scale_120ths}x)");
-                popup_surface.set_scale_factor(new_scale_factor);
+                let render_scale = FractionalScaleConfig::render_scale(new_scale_factor);
+                info!(
+                    "Updating popup scale factor to {} (render scale {}, from {}x)",
+                    new_scale_factor, render_scale, scale_120ths
+                );
+                popup_surface.set_scale_factor(render_scale);
                 popup_surface.request_redraw();
             }
         }

crates/adapters/src/wayland/surfaces/surface_renderer.rs

@@ -1,5 +1,5 @@
 use crate::errors::Result;
-use crate::rendering::femtovg::renderable_window::RenderableWindow;
+use crate::rendering::femtovg::renderable_window::{FractionalScaleConfig, RenderableWindow};
 use crate::wayland::managed_proxies::{
     ManagedWlSurface, ManagedZwlrLayerSurfaceV1, ManagedWpFractionalScaleV1, ManagedWpViewport,
 };
@@ -92,12 +92,19 @@ impl<W: RenderableWindow> SurfaceRenderer<W> {
     ) {
         match mode {
             ScalingMode::FractionalWithViewport => {
-                self.window.set_scale_factor(scale_factor);
-                self.window
-                    .set_size(slint::WindowSize::Logical(slint::LogicalSize::new(
+                let config = FractionalScaleConfig::new(
                     dimensions.logical_width() as f32,
                     dimensions.logical_height() as f32,
-                    )));
+                    scale_factor,
+                );
+                info!(
+                    "FractionalWithViewport: render scale {} (from {}), physical {}x{}",
+                    config.render_scale,
+                    scale_factor,
+                    config.render_physical_size.width,
+                    config.render_physical_size.height
+                );
+                config.apply_to(self.window.as_ref());
             }
             ScalingMode::FractionalOnly => {
                 self.window
@@ -154,15 +161,30 @@ impl<W: RenderableWindow> SurfaceRenderer<W> {
         self.apply_surface_dimensions(dimensions, scale_factor);
     }
 
+    #[allow(clippy::cast_precision_loss)]
     pub fn apply_surface_dimensions(&mut self, dimensions: SurfaceDimensions, scale_factor: f32) {
         let scaling_mode = self.determine_scaling_mode();
 
+        let render_physical_size = match scaling_mode {
+            ScalingMode::FractionalWithViewport => {
+                FractionalScaleConfig::new(
+                    dimensions.logical_width() as f32,
+                    dimensions.logical_height() as f32,
+                    scale_factor,
+                )
+                .render_physical_size
+            }
+            _ => dimensions.to_slint_physical_size(),
+        };
+
         info!(
-            "Updating window size: logical {}x{}, physical {}x{}, scale {}, buffer_scale {}, mode {:?}",
+            "Updating window size: logical {}x{}, physical {}x{}, render_physical {}x{}, scale {}, buffer_scale {}, mode {:?}",
             dimensions.logical_width(),
             dimensions.logical_height(),
             dimensions.physical_width(),
             dimensions.physical_height(),
+            render_physical_size.width,
+            render_physical_size.height,
             scale_factor,
             dimensions.buffer_scale(),
             scaling_mode
@@ -173,7 +195,7 @@ impl<W: RenderableWindow> SurfaceRenderer<W> {
 
         info!("Window physical size: {:?}", self.window.size());
 
-        self.size = dimensions.to_slint_physical_size();
+        self.size = render_physical_size;
         self.logical_size = dimensions.to_slint_logical_size();
         RenderableWindow::request_redraw(self.window.as_ref());
     }