Add position parameter to stack view layers

Can be centered, absolute or relative to the previous layer.
Can be set independently for each axis.

examples/mutation.rs

@@ -1,11 +1,14 @@
 extern crate cursive;
 
 use cursive::Cursive;
-use cursive::view::{IdView, TextView, Dialog, KeyEventView};
+use cursive::view::{IdView, TextView, Dialog, KeyEventView, Position, Offset};
 
 fn show_popup(siv: &mut Cursive) {
 
-    siv.add_layer(Dialog::new(TextView::new("Tak!"))
+    // Let's center the popup horizontally, but offset it down a few rows
+    siv.screen_mut()
+       .add_layer_at(Position::new(Offset::Center, Offset::Parent(3)),
+                     Dialog::new(TextView::new("Tak!"))
                          .button("Change", |s| {
                              // Look for a view tagged "text". We _know_ it's there, so unwrap it.
                              let view = s.find_id::<TextView>("text").unwrap();

src/view/mod.rs

@@ -2,6 +2,15 @@
 
 #[macro_use]mod view_wrapper;
 
+// Essentials components
+mod position;
+mod request;
+mod view_path;
+
+// Helper bases
+mod scroll;
+
+// Views
 mod box_view;
 mod button;
 mod dialog;
@@ -10,14 +19,11 @@ mod full_view;
 mod id_view;
 mod key_event_view;
 mod linear_layout;
-mod request;
 mod shadow_view;
-mod scroll;
 mod select_view;
 mod sized_view;
 mod stack_view;
 mod text_view;
-mod view_path;
 
 
 use std::any::Any;
@@ -26,6 +32,8 @@ use event::{Event, EventResult};
 use vec::Vec2;
 use printer::Printer;
 
+pub use self::position::{Position, Offset};
+
 pub use self::request::{DimensionRequest, SizeRequest};
 pub use self::scroll::ScrollBase;
 

src/view/position.rs

@@ -0,0 +1,57 @@
+use ::vec::{ToVec2, Vec2};
+
+/// Location of the view on screen
+pub struct Position {
+    pub x: Offset,
+    pub y: Offset,
+}
+
+impl Position {
+    pub fn new(x: Offset, y: Offset) -> Self {
+        Position {
+            x: x,
+            y: y,
+        }
+    }
+
+    pub fn center() -> Self {
+        Position::new(Offset::Center, Offset::Center)
+    }
+
+    pub fn absolute<T: ToVec2>(offset: T) -> Self {
+        let offset = offset.to_vec2();
+        Position::new(Offset::Absolute(offset.x), Offset::Absolute(offset.y))
+    }
+
+    pub fn parent<T: ToVec2>(offset: T) -> Self {
+        let offset = offset.to_vec2();
+        Position::new(Offset::Parent(offset.x), Offset::Parent(offset.y))
+    }
+
+    pub fn compute_offset(&self, size: Vec2, available: Vec2, parent: Vec2) -> Vec2 {
+        Vec2::new(self.x.compute_offset(size.x, available.x, parent.x),
+                  self.y.compute_offset(size.y, available.y, parent.y))
+    }
+}
+
+pub enum Offset {
+    /// In the center of the screen
+    Center,
+    /// Place top-left corner at the given absolute coordinates
+    Absolute(usize),
+
+    /// Place top-left corner at the given offset from the previous layer's top-left corner.
+    ///
+    /// If this is the first layer, behaves like `Absolute`.
+    Parent(usize), // TODO: use a signed vec for negative offset?
+}
+
+impl Offset {
+    pub fn compute_offset(&self, size: usize, available: usize, parent: usize) -> usize {
+        match *self {
+            Offset::Center => (available - size) / 2,
+            Offset::Absolute(offset) => offset,
+            Offset::Parent(offset) => parent + offset,
+        }
+    }
+}

src/view/stack_view.rs

@@ -1,7 +1,7 @@
 use std::any::Any;
 
 use vec::Vec2;
-use view::{DimensionRequest, Selector, ShadowView, SizeRequest, View};
+use view::{DimensionRequest, Selector, ShadowView, SizeRequest, View, Position};
 use event::{Event, EventResult};
 use printer::Printer;
 use theme::ColorStyle;
@@ -15,6 +15,7 @@ pub struct StackView {
 struct Layer {
     view: Box<View>,
     size: Vec2,
+    position: Position,
     // Has it received the gift yet?
     virgin: bool,
 }
@@ -31,11 +32,17 @@ impl StackView {
         StackView { layers: Vec::new() }
     }
 
-    /// Add new view on top of the stack.
+    /// Adds new view on top of the stack in the center of the screen.
     pub fn add_layer<T: 'static + View>(&mut self, view: T) {
+        self.add_layer_at(Position::center(), view);
+    }
+
+    /// Adds a view on top of the stack.
+    pub fn add_layer_at<T: 'static + View>(&mut self, position: Position, view: T) {
         self.layers.push(Layer {
             view: Box::new(ShadowView::new(view)),
             size: Vec2::new(0, 0),
+            position: position,
             virgin: true,
         });
     }
@@ -49,13 +56,14 @@ impl StackView {
 impl View for StackView {
     fn draw(&mut self, printer: &Printer) {
         let last = self.layers.len();
+        let mut previous = Vec2::zero();
         printer.with_color(ColorStyle::Primary, |printer| {
             for (i, v) in self.layers.iter_mut().enumerate() {
+                // Place the view
                 // Center the view
-                let size = v.size;
+                let offset = v.position.compute_offset(v.size, printer.size, previous);
-                let offset = (printer.size - size) / 2;
+                previous = offset;
-                // TODO: only draw focus for the top view
+                v.view.draw(&printer.sub_printer(offset, v.size, i + 1 == last));
-                v.view.draw(&printer.sub_printer(offset, size, i + 1 == last));
             }
         });
     }
@@ -68,14 +76,20 @@ impl View for StackView {
     }
 
     fn layout(&mut self, size: Vec2) {
+        // The call has been made, we can't ask for more space anymore.
+        // Let's make do with what we have.
         let req = SizeRequest {
             w: DimensionRequest::AtMost(size.x),
             h: DimensionRequest::AtMost(size.y),
         };
+
         for layer in &mut self.layers {
+            // Give each guy what he asks for, within the budget constraints.
             layer.size = Vec2::min(size, layer.view.get_min_size(req));
             layer.view.layout(layer.size);
+
             // We do it here instead of when adding a new layer because...?
+            // (TODO: try to make it during layer addition)
             if layer.virgin {
                 layer.view.take_focus();
                 layer.virgin = false;