print: Make preview size adaptive

Part-of: <https://gitlab.gnome.org/GNOME/loupe/-/merge_requests/240>

src/widgets/print_preview.rs

@@ -25,64 +25,39 @@ use glib::Properties;
 use gtk::prelude::*;
 use once_cell::sync::OnceCell;
 
-mod imp {
+mod imp_page {
     use super::*;
 
-    #[derive(Debug, Default, Properties)]
-    #[properties(wrapper_type = super::LpPrintPreview)]
-    pub struct LpPrintPreview {
-        #[property(get, set)]
-        print: OnceCell<LpPrint>,
-    }
+    #[derive(Debug, Default)]
+    pub struct LpPrintPreviewPage {}
 
     #[glib::object_subclass]
-    impl ObjectSubclass for LpPrintPreview {
-        const NAME: &'static str = "LpPrintPreview";
-        type Type = super::LpPrintPreview;
+    impl ObjectSubclass for LpPrintPreviewPage {
+        const NAME: &'static str = "LpPrintPreviewPage";
+        type Type = super::LpPrintPreviewPage;
         type ParentType = gtk::Widget;
+
+        fn class_init(klass: &mut Self::Class) {
+            klass.set_css_name("lpprintpreviewpage")
+        }
     }
 
-    impl ObjectImpl for LpPrintPreview {
+    impl ObjectImpl for LpPrintPreviewPage {
         fn constructed(&self) {
             self.parent_constructed();
-            self.obj().set_halign(gtk::Align::Center);
-            self.obj().set_valign(gtk::Align::Start);
             self.obj().set_overflow(gtk::Overflow::Hidden);
         }
-
-        fn properties() -> &'static [glib::ParamSpec] {
-            Self::derived_properties()
-        }
-        fn set_property(&self, id: usize, value: &glib::Value, pspec: &glib::ParamSpec) {
-            self.derived_set_property(id, value, pspec)
-        }
-        fn property(&self, id: usize, pspec: &glib::ParamSpec) -> glib::Value {
-            self.derived_property(id, pspec)
-        }
     }
 
-    impl WidgetImpl for LpPrintPreview {
-        fn measure(&self, orientation: gtk::Orientation, _for_size: i32) -> (i32, i32, i32, i32) {
-            let (width, height) = self.display_paper_dimensions();
-
-            let size = match orientation {
-                gtk::Orientation::Horizontal => width,
-                _ => height,
-            };
-
-            (size, size, -1, -1)
-        }
-
+    impl WidgetImpl for LpPrintPreviewPage {
         fn snapshot(&self, snapshot: &gtk::Snapshot) {
-            let obj = self.obj();
-
             snapshot.save();
 
-            let scale = obj.print().user_scale() * self.display_scale();
-            let margin_left = obj.print().effective_margin_left() * self.display_scale();
-            let margin_top = obj.print().effective_margin_top() * self.display_scale();
+            let scale = self.print().user_scale() * self.display_scale();
+            let margin_left = self.print().effective_margin_left() * self.display_scale();
+            let margin_top = self.print().effective_margin_top() * self.display_scale();
 
-            if let Some(texture) = self.obj().print().image().print_data(scale) {
+            if let Some(texture) = self.print().image().print_data(scale) {
                 let area = graphene::Rect::new(
                     margin_left as f32,
                     margin_top as f32,
@@ -106,34 +81,108 @@ mod imp {
         }
     }
 
-    impl LpPrintPreview {
-        /// Returns scale factor from print pixel to preview size
-        fn display_scale(&self) -> f64 {
-            let print = self.obj().print();
-
-            let height = print.page_setup().paper_height(gtk::Unit::Inch) * print.dpi();
-            let width = print.page_setup().paper_width(gtk::Unit::Inch) * print.dpi();
-
-            300. / f64::max(width, height)
+    impl LpPrintPreviewPage {
+        fn preview(&self) -> super::LpPrintPreview {
+            self.obj().parent().unwrap().downcast().unwrap()
         }
 
-        /// Returns total preview size in pixels
-        fn display_paper_dimensions(&self) -> (i32, i32) {
+        fn print(&self) -> LpPrint {
+            self.preview().print()
+        }
+
+        fn display_scale(&self) -> f64 {
+            let print = self.print();
+            let page_width = print.page_setup().paper_width(gtk::Unit::Inch) * print.dpi();
+            self.obj().width() as f64 / page_width
+        }
+    }
+}
+
+mod imp {
+    use super::*;
+
+    #[derive(Debug, Default, Properties)]
+    #[properties(wrapper_type = super::LpPrintPreview)]
+    pub struct LpPrintPreview {
+        #[property(get, set)]
+        print: OnceCell<LpPrint>,
+        page: LpPrintPreviewPage,
+    }
+
+    #[glib::object_subclass]
+    impl ObjectSubclass for LpPrintPreview {
+        const NAME: &'static str = "LpPrintPreview";
+        type Type = super::LpPrintPreview;
+        type ParentType = gtk::Widget;
+
+        fn class_init(klass: &mut Self::Class) {
+            klass.set_css_name("lpprintpreview")
+        }
+    }
+
+    impl ObjectImpl for LpPrintPreview {
+        fn constructed(&self) {
+            self.parent_constructed();
+
+            self.page.insert_after(&*self.obj(), gtk::Widget::NONE);
+        }
+
+        fn properties() -> &'static [glib::ParamSpec] {
+            Self::derived_properties()
+        }
+        fn set_property(&self, id: usize, value: &glib::Value, pspec: &glib::ParamSpec) {
+            self.derived_set_property(id, value, pspec)
+        }
+        fn property(&self, id: usize, pspec: &glib::ParamSpec) -> glib::Value {
+            self.derived_property(id, pspec)
+        }
+    }
+
+    impl WidgetImpl for LpPrintPreview {
+        fn size_allocate(&self, width: i32, height: i32, baseline: i32) {
+            let (page_width, page_height) = self.aspect_preserving_size(width, height);
+
+            self.page.size_allocate(
+                &gdk::Rectangle::new(
+                    (width - page_width) / 2,
+                    (height - page_height) / 2,
+                    page_width,
+                    page_height,
+                ),
+                baseline,
+            );
+
+            self.page.queue_draw();
+        }
+    }
+
+    impl LpPrintPreview {
+        fn aspect_preserving_size(&self, for_width: i32, for_height: i32) -> (i32, i32) {
             let print = self.obj().print();
 
-            let height = print.page_setup().paper_height(gtk::Unit::Inch) * print.dpi();
-            let width = print.page_setup().paper_width(gtk::Unit::Inch) * print.dpi();
+            let ratio = (print.page_setup().paper_width(gtk::Unit::Inch)
+                / print.page_setup().paper_height(gtk::Unit::Inch)) as f32;
 
-            let scale = self.display_scale();
-
-            ((width * scale) as i32, (height * scale) as i32)
+            if ratio > for_width as f32 / for_height as f32 {
+                (for_width, (for_width as f32 / ratio) as i32)
+            } else {
+                ((for_height as f32 * ratio) as i32, for_height)
+            }
         }
     }
 }
 glib::wrapper! {
-    pub struct LpPrintPreview(ObjectSubclass<imp::LpPrintPreview>)
+    pub struct LpPrintPreviewPage(ObjectSubclass<imp_page::LpPrintPreviewPage>)
         @extends gtk::Widget;
 }
 
-#[gtk::template_callbacks]
-impl LpPrintPreview {}
+impl Default for LpPrintPreviewPage {
+    fn default() -> Self {
+        glib::Object::new()
+    }
+}
+
+glib::wrapper! {
+    pub struct LpPrintPreview(ObjectSubclass<imp::LpPrintPreview>)
+        @extends gtk::Widget;
+}