From 3ece8e36bd7c1aa08374ff8ffa0f7206976746fd Mon Sep 17 00:00:00 2001
From: Arne Dußin
Date: Wed, 28 Oct 2020 20:49:51 +0100
Subject: Add possibility to draw rectangles

---
 src/main.rs | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 92 insertions(+), 6 deletions(-)

(limited to 'src')

diff --git a/src/main.rs b/src/main.rs
index faa5b7d..e6c85ea 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,31 +1,102 @@
 use piston_window::grid::Grid;
+use piston_window::rectangle::{Border, Rectangle};
 use piston_window::*;
 use sdl2_window::Sdl2Window;
+use std::cmp;
 
-pub const BLACK: [f32; 4] = [0.0, 0.0, 0.0, 0.8];
+pub const MIN_PIXELS_PER_M: f64 = 0.5;
+pub const MAX_PIXELS_PER_M: f64 = 10_000.;
+pub const STANDARD_PIXELS_PER_M: f64 = 64.;
+
+/// Helper function to turn two given points into a rectangle. The order of the two points is not
+/// important, they are considered two endpoints of a diagonal and therefore identify the rectangle
+/// unambiguously.
+fn bounding_box(p0: [f64; 2], p1: [f64; 2]) -> [f64; 4] {
+    let min_x = p0[0].min(p1[0]);
+    let min_y = p0[1].min(p1[1]);
+    let max_x = p0[0].max(p1[0]);
+    let max_y = p0[1].max(p1[1]);
+
+    [min_x, min_y, max_x - min_x, max_y - min_y]
+}
 
 fn main() {
     let mut window: PistonWindow<Sdl2Window> = WindowSettings::new("Hello there!", [1000, 1000])
         .build()
         .expect("Could not initialise window");
 
-    let mut pixels_per_m = 64.;
+    // The amount of on-screen pixels used to represent a meter of actual terrain.
+    let mut pixels_per_m = STANDARD_PIXELS_PER_M;
+
+    /* Create a rectangle that is used to draw all rectangles that were created by the user. It has
+     * a thicc blacc border and white colour.
+     */
+    let render_rect = Rectangle::new([0.7, 0.7, 0.7, 1.]).border(Border {
+        color: [0.5, 0.5, 0.5, 1.],
+        radius: 2.,
+    });
+    // The point the user has clicked. This is where they want the rectangle to start.
+    let mut starting_rect_point: Option<[f64; 2]> = None;
+    let mut rectangles = Vec::new();
+
+    // Line used to draw the square grid.
+    let grid_line = Line::new([1., 1., 1., 0.3], 1.5);
 
-    let grid_line = Line::new(BLACK, 1.5);
+    let mut mouse_pos = [0., 0.];
     let mut events = Events::new(EventSettings::new().lazy(true));
     while let Some(e) = events.next(&mut window) {
+        // Update the mouse cursor position
+        e.mouse_cursor(|pos| {
+            mouse_pos = pos;
+        });
+
+        // The zoom factor is changed with the mouse wheel.
         e.mouse_scroll(|[_, y]| {
-            if y < 0. {
+            let scale_changed = if y < 0. && MAX_PIXELS_PER_M > pixels_per_m {
                 pixels_per_m *= 1.2;
-            } else if y > 0. {
+                true
+            } else if y > 0. && MIN_PIXELS_PER_M < pixels_per_m {
                 pixels_per_m /= 1.2;
+                true
+            } else {
+                false
+            };
+
+            /* Make sure that the scale factors stay very close to the normal scale factors, even
+             * when the user zooms in and out very often, at least when they zoom over the standard
+             * zoom factor.
+             */
+            if pixels_per_m > STANDARD_PIXELS_PER_M - 5.
+                && pixels_per_m < STANDARD_PIXELS_PER_M + 5.
+            {
+                pixels_per_m = STANDARD_PIXELS_PER_M;
+            }
+
+            // Notify the user of the change if there was any
+            if scale_changed {
+                println!("Changed scale to {} pixels per m.", pixels_per_m);
             }
         });
 
+        // Handle drawing a rectangle or finishing the rectangle when clicking with the mouse.
+        if let Some(Button::Mouse(MouseButton::Left)) = e.press_args() {
+            if let Some(first_point) = starting_rect_point {
+                rectangles.push(bounding_box(first_point, mouse_pos));
+                starting_rect_point = None;
+            } else {
+                starting_rect_point = Some(mouse_pos);
+            }
+        }
+
+        // Close the window when the user presses escape
         if let Some(Button::Keyboard(Key::Escape)) = e.press_args() {
             window.set_should_close(true);
         }
 
+        /* Update the Grid draw size to the actual window draw size.
+         * TODO: Currently, the window canvas draw size is never updated. This has to be changed in
+         * order to deal with the user resizing the window.
+         */
         let win_size = window.draw_size();
         let grid = Grid {
             cols: (win_size.width / pixels_per_m) as u32 + 1,
@@ -34,9 +105,24 @@ fn main() {
         };
 
         window.draw_2d(&e, |c, g, _device| {
-            clear([1.0; 4], g);
+            clear([0.4, 0.2, 0., 1.], g);
 
             grid.draw(&grid_line, &c.draw_state, c.transform, g);
+
+            // Draw all rectangles that are part of the map
+            for &rect in &rectangles {
+                render_rect.draw(rect, &c.draw_state, c.transform, g);
+            }
+
+            // Draw the current rectangle that is being drawn, but not part of the map
+            if let Some(starting_rect_point) = starting_rect_point {
+                render_rect.draw(
+                    bounding_box(starting_rect_point, mouse_pos),
+                    &c.draw_state,
+                    c.transform,
+                    g,
+                );
+            }
         });
     }
 }
-- 
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