image/zoom: Allow levels smaller best-fit from menu

Closes #437, #414

src/widgets/image.rs

@@ -124,11 +124,16 @@ const SMALL_SCREEN_AREA: f64 = 1280. * 1024.;
 /// For small monitors occupy 80% of the screen area
 const SMALL_OCCUPY_SCREEN: f64 = 0.8;
 
-#[derive(Default, Debug, Clone, Copy)]
+#[derive(Default, Debug, Clone, Copy, glib::Variant, glib::Enum, PartialEq, Eq)]
+#[enum_type(name = "LpFitMode")]
 pub enum FitMode {
     #[default]
     BestFit,
     LargeFit,
+    /// Allow zoom to be set smaller than best fit. Allow arbitrary zoom
+    /// operations until zoom is larger than best-fit, which resets to `BestFit`
+    /// mode.`
+    ExactVolatile,
 }
 
 mod imp {
@@ -199,6 +204,7 @@ mod imp {
         #[property(get, set)]
         pub(super) best_fit: Cell<bool>,
         /// Determines what `best-fit` does
+        #[property(get, set=Self::set_fit_mode, builder(FitMode::default()))]
         pub(super) fit_mode: Cell<FitMode>,
         /// Max zoom level is reached, stored to only send signals on change
         #[property(get, set)]

src/widgets/image/input_handling.rs

@@ -339,7 +339,9 @@ impl imp::LpImage {
                 log::debug!("Zoom gesture end");
 
                 let rotation_target = (obj.rotation() / 90.).round() * 90.;
-                if obj.zoom() < imp.zoom_level_best_fit_for_rotation(rotation_target) {
+                if obj.zoom() < imp.zoom_level_best_fit_for_rotation(rotation_target)
+                    && obj.fit_mode() != FitMode::ExactVolatile
+                {
                     obj.zoom_to(imp.zoom_level_best_fit_for_rotation(rotation_target));
                 } else {
                     // rubberband if over highest zoom level and sets `zoom_target`

src/widgets/image/zoom.rs

@@ -50,7 +50,7 @@ impl imp::LpImage {
             // Do not allow to zoom larger than original size
             FitMode::BestFit => 1.,
             // Allow arbitrary zoom
-            FitMode::LargeFit => f64::MAX,
+            FitMode::LargeFit | FitMode::ExactVolatile => f64::MAX,
         };
 
         let default_zoom = if texture_aspect_ratio > widget_aspect_ratio {
@@ -138,7 +138,7 @@ impl imp::LpImage {
             );
         }
 
-        if zoom < self.zoom_level_best_fit() {
+        if zoom < self.zoom_level_best_fit() && obj.fit_mode() == FitMode::BestFit {
             let minimum = self.zoom_level_best_fit();
             let max_deviation = minimum / ZOOM_FACTOR_MAX_RUBBERBAND;
             let deviation = zoom / minimum;
@@ -222,7 +222,14 @@ impl imp::LpImage {
             self.zoom_level_best_fit()
         };
 
-        if zoom <= extended_best_fit_threshold {
+        // Reset fit mode if entering in the usual zoom levels again
+        if obj.fit_mode() == FitMode::ExactVolatile
+            && zoom >= f64::min(1.0, self.zoom_level_best_fit())
+        {
+            obj.set_fit_mode(FitMode::BestFit)
+        }
+
+        if zoom <= extended_best_fit_threshold && obj.fit_mode() != FitMode::ExactVolatile {
             zoom = self.zoom_level_best_fit();
             obj.set_best_fit(true);
         } else {
@@ -290,6 +297,13 @@ impl imp::LpImage {
             animation
         })
     }
+
+    pub fn set_fit_mode(&self, fit_mode: FitMode) {
+        self.fit_mode.replace(fit_mode);
+        if fit_mode != FitMode::ExactVolatile {
+            self.configure_best_fit();
+        }
+    }
 }
 
 impl LpImage {
@@ -348,19 +362,19 @@ impl LpImage {
         self.imp().zoom_to_full(zoom, true, false, false);
     }
 
-    /// Same as `zoom_to_exact` but zoom to center
-    pub fn zoom_to_exact_center(&self, zoom: f64) {
+    pub fn zoom_to_no_best_fit(&self, zoom: f64) {
+        self.set_fit_mode(FitMode::ExactVolatile);
+        self.set_best_fit(false);
+        self.imp().zoom_to_full(zoom, true, false, false);
+    }
+
+    pub fn zoom_to_center_no_best_fit(&self, zoom: f64) {
+        self.set_fit_mode(FitMode::ExactVolatile);
+        self.set_best_fit(false);
         self.imp().zoom_to_full(zoom, true, false, true);
     }
 
     pub fn is_best_fit(&self) -> bool {
         self.imp().best_fit.get()
     }
-
-    pub fn set_fit_mode(&self, fit_mode: FitMode) {
-        let imp = self.imp();
-
-        imp.fit_mode.replace(fit_mode);
-        imp.configure_best_fit();
-    }
 }

src/widgets/image_view.rs

@@ -262,7 +262,7 @@ mod imp {
                     };
 
                     if let Some(image) = obj.current_image() {
-                        image.zoom_to_exact_center(value);
+                        image.zoom_to_center_no_best_fit(value);
                     }
 
                     // Close popover after click
@@ -276,7 +276,7 @@ mod imp {
                 move |_| {
                     if let Some(page) = obj.current_page() {
                         if let Some(value) = obj.zoom_value_f64() {
-                            page.image().zoom_to_exact(value);
+                            page.image().zoom_to_no_best_fit(value);
                         }
                     }
                 }