image: Limit SVG zoom to RSVG limits

See <https://gitlab.gnome.org/GNOME/librsvg/-/issues/938>
for details about the problem.

Closes #88

src/decoder/formats/mod.rs

@@ -4,6 +4,6 @@ mod svg;
 
 pub use heif::Heif;
 pub use image_rs_other::ImageRsOther;
-pub use svg::Svg;
+pub use svg::{Svg, RSVG_MAX_SIZE};
 
 use super::{Decoder, UpdateSender};

src/decoder/formats/svg.rs

@@ -11,6 +11,10 @@ use gtk::prelude::*;
 use std::path::PathBuf;
 use std::sync::Arc;
 
+/// Current librsvg limit on maximum dimensions. See
+/// <https://gitlab.gnome.org/GNOME/librsvg/-/issues/938>
+pub const RSVG_MAX_SIZE: u32 = 32_767;
+
 #[derive(Debug)]
 pub struct Svg {
     thread_handle: std::thread::JoinHandle<()>,
@@ -106,9 +110,7 @@ impl Svg {
                                 tile_instructions.tiling.scaled_dimensions();
 
                             // librsvg does not currently support larger images
-                            //
+                            if total_height > RSVG_MAX_SIZE || total_width > RSVG_MAX_SIZE {
-                            // TODO: We are only creating tiles, maybe this check in librsvg is wrong?
-                            if total_height > 32_767 || total_width > 32_767 {
                                 continue;
                             }
 

src/decoder/mod.rs

@@ -15,6 +15,8 @@ use gtk::graphene;
 use std::io::Read;
 use std::sync::Arc;
 
+pub use formats::RSVG_MAX_SIZE;
+
 #[derive(Clone, Copy, Debug)]
 pub enum ImageFormat {
     ImageRs(image_rs::ImageFormat),

src/widgets/image.rs

@@ -87,6 +87,7 @@ mod imp {
         pub file_monitor: RefCell<Option<gio::FileMonitor>>,
         pub tiles: Arc<ArcSwap<tiling::TilingStore>>,
         pub decoder: RefCell<Option<Arc<Decoder>>>,
+        pub format: RefCell<Option<decoder::ImageFormat>>,
 
         /// Set to true when image is ready for displaying
         pub is_loaded: Cell<bool>,
@@ -710,8 +711,8 @@ impl LpImage {
             DecoderUpdate::Error(err) => {
                 self.set_error(err);
             }
-            DecoderUpdate::Format(_) => {
+            DecoderUpdate::Format(format) => {
-                // TODO: Store and use in image properties
+                imp.format.replace(Some(format));
             }
         }
     }
@@ -961,14 +962,29 @@ impl LpImage {
         decoder::tiling::zoom_normalize(self.zoom())
     }
 
+    /// Maximal zoom allowed for this image
+    fn max_zoom(&self) -> f64 {
+        if let Some(decoder::ImageFormat::Svg) = dbg!(self.format()) {
+            let (width, height) = self.original_dimensions();
+            // Avoid division by 0
+            let long_side = f64::max(1., i32::max(width, height) as f64);
+            // Limit to maz size supported by rsvg
+            f64::min(MAX_ZOOM_LEVEL, decoder::RSVG_MAX_SIZE as f64 / long_side)
+        } else {
+            MAX_ZOOM_LEVEL
+        }
+    }
+
     /// Set zoom level aiming for given position or center if not available
     fn set_zoom_aiming(&self, mut zoom: f64, aiming: Option<(f64, f64)>) {
+        let max_zoom = self.max_zoom();
+
         // allow some deviation from max value for rubberbanding
-        if zoom > MAX_ZOOM_LEVEL {
+        if zoom > max_zoom {
-            let max_deviation = MAX_ZOOM_LEVEL * ZOOM_FACTOR_MAX_RUBBERBAND;
+            let max_deviation = max_zoom * ZOOM_FACTOR_MAX_RUBBERBAND;
-            let deviation = zoom / MAX_ZOOM_LEVEL;
+            let deviation = zoom / max_zoom;
             zoom = f64::min(
-                MAX_ZOOM_LEVEL * deviation.powf(RUBBERBANDING_EXPONENT),
+                max_zoom * deviation.powf(RUBBERBANDING_EXPONENT),
                 max_deviation,
             );
         }
@@ -1136,8 +1152,9 @@ impl LpImage {
 
     /// Zoom to specific level with animation
     pub fn zoom_to(&self, mut zoom: f64) {
-        if zoom >= MAX_ZOOM_LEVEL {
+        let max_zoom = self.max_zoom();
-            zoom = MAX_ZOOM_LEVEL;
+        if zoom >= max_zoom {
+            zoom = max_zoom;
             self.set_max_zoom(true);
         } else {
             self.set_max_zoom(false);
@@ -1413,6 +1430,11 @@ impl LpImage {
         Some(gdk::ContentProvider::for_value(&list.to_value()))
     }
 
+    /// Image format
+    pub fn format(&self) -> Option<decoder::ImageFormat> {
+        *self.imp().format.borrow()
+    }
+
     /// Returns decoding error if one occured
     pub fn error(&self) -> Option<String> {
         self.imp().error.borrow().clone()