image: Reorganize into several sub-modules

src/widgets/image/pan.rs

@@ -0,0 +1,49 @@
+// Copyright (c) 2023 Sophie Herold
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+use super::*;
+
+impl LpImage {
+    /// Stepwise scrolls inside an image when zoomed in
+    pub fn pan(&self, direction: &gtk::PanDirection) {
+        let sign = match direction {
+            gtk::PanDirection::Left | gtk::PanDirection::Up => -1.,
+            gtk::PanDirection::Right | gtk::PanDirection::Down => 1.,
+            _ => {
+                log::error!("Unknown pan direction {direction:?}");
+                return;
+            }
+        };
+
+        let (adjustment, max) = match direction {
+            gtk::PanDirection::Left | gtk::PanDirection::Right => {
+                (self.hadjustment(), self.max_hadjustment_value())
+            }
+            gtk::PanDirection::Up | gtk::PanDirection::Down => {
+                (self.vadjustment(), self.max_vadjustment_value())
+            }
+            _ => {
+                log::error!("Unknown pan direction {direction:?}");
+                return;
+            }
+        };
+
+        let value = (adjustment.value() + sign * adjustment.step_increment()).clamp(0., max);
+
+        adjustment.set_value(value);
+    }
+}