Better define the meaning of `SizeHint` (#7079)

crates/egui/src/load.rs

@@ -151,14 +151,21 @@ pub enum SizeHint {
     /// Scale original size by some factor.
     Scale(OrderedFloat<f32>),
 
-    /// Scale to width.
+    /// Scale to exactly this pixel width, keeping the original aspect ratio.
     Width(u32),
 
-    /// Scale to height.
+    /// Scale to exactly this pixel height, keeping the original aspect ratio.
     Height(u32),
 
-    /// Scale to size.
-    Size(u32, u32),
+    /// Scale to this pixel size.
+    Size {
+        width: u32,
+        height: u32,
+
+        /// If true, the image will be as large as possible
+        /// while still fitting within the given width/height.
+        maintain_aspect_ratio: bool,
+    },
 }
 
 impl Default for SizeHint {
@@ -168,13 +175,6 @@ impl Default for SizeHint {
     }
 }
 
-impl From<Vec2> for SizeHint {
-    #[inline]
-    fn from(value: Vec2) -> Self {
-        Self::Size(value.x.round() as u32, value.y.round() as u32)
-    }
-}
-
 /// Represents a byte buffer.
 ///
 /// This is essentially `Cow<'static, [u8]>` but with the `Owned` variant being an `Arc`.

crates/egui/src/widgets/image.rs

@@ -384,7 +384,11 @@ impl<'a> Image<'a> {
         let texture = self.source(ui.ctx()).clone().load(
             ui.ctx(),
             self.texture_options,
-            SizeHint::Size(pixel_size.x as _, pixel_size.y as _),
+            SizeHint::Size {
+                width: pixel_size.x as _,
+                height: pixel_size.y as _,
+                maintain_aspect_ratio: false, // no - just get exactly what we asked for
+            },
         );
 
         paint_texture_load_result(
@@ -481,22 +485,30 @@ impl ImageFit {
 impl ImageSize {
     /// Size hint for e.g. rasterizing an svg.
     pub fn hint(&self, available_size: Vec2, pixels_per_point: f32) -> SizeHint {
-        let point_size = match self.fit {
+        let Self {
+            maintain_aspect_ratio,
+            max_size,
+            fit,
+        } = *self;
+
+        let point_size = match fit {
             ImageFit::Original { scale } => {
                 return SizeHint::Scale((pixels_per_point * scale).ord())
             }
             ImageFit::Fraction(fract) => available_size * fract,
             ImageFit::Exact(size) => size,
         };
-        let point_size = point_size.at_most(self.max_size);
+        let point_size = point_size.at_most(max_size);
 
         let pixel_size = pixels_per_point * point_size;
 
         // `inf` on an axis means "any value"
         match (pixel_size.x.is_finite(), pixel_size.y.is_finite()) {
-            (true, true) => {
-                SizeHint::Size(pixel_size.x.round() as u32, pixel_size.y.round() as u32)
-            }
+            (true, true) => SizeHint::Size {
+                width: pixel_size.x.round() as u32,
+                height: pixel_size.y.round() as u32,
+                maintain_aspect_ratio,
+            },
             (true, false) => SizeHint::Width(pixel_size.x.round() as u32),
             (false, true) => SizeHint::Height(pixel_size.y.round() as u32),
             (false, false) => SizeHint::Scale(pixels_per_point.ord()),

crates/egui_extras/src/image.rs

@@ -255,43 +255,51 @@ pub fn load_svg_bytes_with_size(
     size_hint: Option<SizeHint>,
     options: &resvg::usvg::Options<'_>,
 ) -> Result<egui::ColorImage, String> {
-    use resvg::tiny_skia::{IntSize, Pixmap};
-    use resvg::usvg::{Transform, Tree};
+    use egui::Vec2;
+    use resvg::{
+        tiny_skia::Pixmap,
+        usvg::{Transform, Tree},
+    };
 
     profiling::function_scope!();
 
     let rtree = Tree::from_data(svg_bytes, options).map_err(|err| err.to_string())?;
 
-    let size = rtree.size().to_int_size();
+    let original_size = Vec2::new(rtree.size().width(), rtree.size().height());
+
     let scaled_size = match size_hint {
-        None => size,
-        Some(SizeHint::Size(w, h)) => size.scale_to(
-            IntSize::from_wh(w, h).ok_or_else(|| format!("Failed to scale SVG to {w}x{h}"))?,
-        ),
-        Some(SizeHint::Height(h)) => size
-            .scale_to_height(h)
-            .ok_or_else(|| format!("Failed to scale SVG to height {h}"))?,
-        Some(SizeHint::Width(w)) => size
-            .scale_to_width(w)
-            .ok_or_else(|| format!("Failed to scale SVG to width {w}"))?,
-        Some(SizeHint::Scale(z)) => {
-            let z_inner = z.into_inner();
-            size.scale_by(z_inner)
-                .ok_or_else(|| format!("Failed to scale SVG by {z_inner}"))?
+        None => original_size,
+        Some(SizeHint::Size {
+            width,
+            height,
+            maintain_aspect_ratio,
+        }) => {
+            if maintain_aspect_ratio {
+                // As large as possible, without exceeding the given size:
+                let mut size = original_size;
+                size *= width as f32 / original_size.x;
+                if size.y > height as f32 {
+                    size *= height as f32 / size.y;
+                }
+                size
+            } else {
+                Vec2::new(width as _, height as _)
+            }
         }
+        Some(SizeHint::Height(h)) => original_size * (h as f32 / original_size.y),
+        Some(SizeHint::Width(w)) => original_size * (w as f32 / original_size.x),
+        Some(SizeHint::Scale(scale)) => scale.into_inner() * original_size,
     };
 
-    let (w, h) = (scaled_size.width(), scaled_size.height());
+    let scaled_size = scaled_size.round();
+    let (w, h) = (scaled_size.x as u32, scaled_size.y as u32);
 
     let mut pixmap =
         Pixmap::new(w, h).ok_or_else(|| format!("Failed to create SVG Pixmap of size {w}x{h}"))?;
 
     resvg::render(
         &rtree,
-        Transform::from_scale(
-            w as f32 / size.width() as f32,
-            h as f32 / size.height() as f32,
-        ),
+        Transform::from_scale(w as f32 / original_size.x, h as f32 / original_size.y),
         &mut pixmap.as_mut(),
     );