Scrollview: move offset to keep important area in view

src/printer.rs

@@ -96,11 +96,12 @@ impl<'a> Printer<'a> {
     // We don't want people to start calling prints in parallel?
     /// Prints some text at the given position relative to the window.
     pub fn print<S: Into<Vec2>>(&self, start: S, text: &str) {
+        // Where we are asked to start printing. Oh boy.
         let start = start.into();
 
         // We accept requests between `content_offset` and
-        // `content_offset + size`
+        // `content_offset + output_size`.
-        if start >= self.output_size + self.content_offset {
+        if !(start < (self.output_size + self.content_offset)) {
             return;
         }
 

src/views/button.rs

@@ -4,6 +4,7 @@ use event::*;
 use theme::ColorStyle;
 use unicode_width::UnicodeWidthStr;
 use vec::Vec2;
+use rect::Rect;
 use view::View;
 use {Cursive, Printer, With};
 
@@ -139,8 +140,7 @@ impl View for Button {
             ColorStyle::highlight()
         };
 
-        let offset =
+        let offset = HAlign::Center.get_offset(self.label.width(), printer.size.x);
-            HAlign::Center.get_offset(self.label.len(), printer.size.x);
 
         printer.with_color(style, |printer| {
             printer.print((offset, 0), &self.label);
@@ -175,4 +175,11 @@ impl View for Button {
     fn take_focus(&mut self, _: Direction) -> bool {
         self.enabled
     }
+
+    fn important_area(&self, view_size: Vec2) -> Rect {
+        let width = self.label.width();
+        let offset = HAlign::Center.get_offset(width, view_size.x);
+
+        Rect::from_size((offset, 0), (width, 1))
+    }
 }

src/views/scroll_view.rs

@@ -182,13 +182,16 @@ where
             EventResult::Ignored => {
                 // If it's an arrow, try to scroll in the given direction.
                 // If it's a mouse scroll, try to scroll as well.
+                // Also allow Ctrl+arrow to move the view without moving selection.
                 match event {
+                    Event::Ctrl(Key::Up) |
                     Event::Key(Key::Up)
                         if self.enabled.y && self.offset.y > 0 =>
                     {
                         self.offset.y -= 1;
                         EventResult::Consumed(None)
                     }
+                    Event::Ctrl(Key::Down) |
                     Event::Key(Key::Down)
                         if self.enabled.y
                             && (self.offset.y + self.last_size.y
@@ -197,12 +200,14 @@ where
                         self.offset.y += 1;
                         EventResult::Consumed(None)
                     }
+                    Event::Ctrl(Key::Left) |
                     Event::Key(Key::Left)
                         if self.enabled.x && self.offset.x > 0 =>
                     {
                         self.offset.x -= 1;
                         EventResult::Consumed(None)
                     }
+                    Event::Ctrl(Key::Right) |
                     Event::Key(Key::Right)
                         if self.enabled.x
                             && (self.offset.x + self.last_size.x
@@ -214,7 +219,24 @@ where
                     _ => EventResult::Ignored,
                 }
             }
-            other => other,
+            other => {
+                // Fix offset?
+                let important = self.inner.important_area(self.inner_size);
+
+                // The furthest top-left we can go
+                let top_left = (important.bottom_right() + (1,1)).saturating_sub(self.last_size);
+                // The furthest bottom-right we can go
+                let bottom_right = important.top_left();
+
+                // "top_left < bottom_right" is NOT guaranteed
+                // if the child is larger than the view.
+                let offset_min = Vec2::min(top_left, bottom_right);
+                let offset_max = Vec2::max(top_left, bottom_right);
+
+                self.offset = self.offset.or_max(offset_min).or_min(offset_max);
+
+                other
+            },
         }
     }