add middle mouse pan

1 files changed, 13 insertions, 0 deletions

diff --git a/src/app.rs b/src/app.rs
index fc7f736..70d68b8 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -68,6 +68,7 @@ pub struct AppState<'ctx> {
     pub ttf_context: &'ctx Sdl2TtfContext,
     pub undo_stack: UndoStack<ModifyRecord>,
     pub zoom: u8,
+    pub pan_start: Point,
 }
 
 // private actions on appstate
@@ -678,6 +679,7 @@ impl<'ctx> AppState<'ctx> {
             mouse: (0, 0),
             pixmap,
             start: Point::new(60, 60),
+            pan_start: Point::new(0, 0),
             symmetry: Default::default(),
             ttf_context,
             undo_stack: UndoStack::new(),
@@ -821,6 +823,12 @@ impl<'ctx> AppState<'ctx> {
                                         .unwrap_or(0),
                                 );
                             }
+                            Event::MouseButtonDown {
+                                x,
+                                y,
+                                mouse_btn: MouseButton::Middle,
+                                ..
+                            } => self.pan_start = Point::from((x, y)),
                             // start of operation
                             Event::MouseButtonDown {
                                 x, y, mouse_btn, ..
@@ -962,6 +970,11 @@ impl<'ctx> AppState<'ctx> {
                                         }
                                         _ => (),
                                     }
+                                } else if mousestate.is_mouse_button_pressed(MouseButton::Middle) {
+                                    let pan_end = Point::from((x, y));
+                                    let shift = pan_end - self.pan_start;
+                                    self.start += shift;
+                                    self.pan_start = pan_end;
                                 }
                             }
                             // end of operation