commit 8d54015a5d5149e9178aede386d9caca5c7f25cf
Author: Cameron Reikes <cameronreikes@gmail.com>
Date:   Mon Jan 23 15:17:22 2023 -0800

    Zooming and rect/line drawing

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..701ae90
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+physics.exe
+*.pdb
+.build/
diff --git a/physics.jai b/physics.jai
new file mode 100644
index 0000000..b60c5d5
--- /dev/null
+++ b/physics.jai
@@ -0,0 +1,146 @@
+#import "Basic";
+#import "Math";
+#import "Window_Creation";
+Input :: #import "Input";
+Simp :: #import "Simp";
+
+window_width  : s32 = 1280;
+window_height : s32 = 720;
+
+xy :: (x: int, y: int) -> Vector2 {
+    return xy(cast(float)x, cast(float)y);
+}
+drawing_in_world_space: bool = false;
+line :: (_from: Vector2, _to: Vector2, width: float = 1.0) {
+    from := _from;
+    to := _to;
+    if drawing_in_world_space {
+        from = world_to_screen(from);
+        to = world_to_screen(to);
+    }
+    Simp.set_shader_for_color();
+    normal := rotate(unit_vector(to - from), PI/2.0);
+    Simp.immediate_quad(from + normal*width, from - normal*width, to + normal*width, to - normal*width);
+}
+
+Rect :: struct {
+    pos, halfsize: Vector2; // pos is in world space
+    rotation: float;
+};
+draw_rect :: (using r: Rect) {
+    facing_to_right := rotate(xy(halfsize.x,0.0), rotation);
+    facing_to_up    := rotate(xy(0.0,halfsize.y), rotation);
+
+    upper_right := pos + facing_to_right + facing_to_up;
+    upper_left  := pos - facing_to_right + facing_to_up;
+    lower_left  := pos - facing_to_right - facing_to_up;
+    lower_right := pos + facing_to_right - facing_to_up;
+
+    line(upper_left, upper_right);
+    line(upper_right, lower_right);
+    line(lower_right, lower_left);
+    line(lower_left, upper_left);
+}
+
+mouse :: () -> Vector2 {
+    x, y := get_mouse_pointer_position();
+    pos: Vector2 = xy(cast(float)x, cast(float)y);
+
+    // simp is lower left is (0, 0) and y+ is up
+    pos.y = window_height - pos.y;
+
+    return pos;
+}
+
+Camera :: struct {
+    pos: Vector2;
+    zoom: float = 1.0;
+};
+
+camera : Camera; 
+screen_to_world :: (screen: Vector2) -> Vector2 {
+    using camera;
+    return (screen + pos)*zoom;
+}
+world_to_screen :: (world: Vector2) -> Vector2 {
+    using camera;
+    // world = (screen + pos)*zoom;
+    // world/zoom = screen + pos;
+    // world/zoom - pos = screen;
+    return (world/zoom) - pos;
+}
+
+main :: () {
+    window := create_window(window_width, window_height, "A Window");
+    // Actual render size in pixels can be different from the window dimensions we specified above (for example on high-resolution displays on macOS/iOS).
+    window_width, window_height = Simp.get_render_dimensions(window);
+
+    Simp.set_render_target(window);
+
+    rects: [..]Rect;
+    array_add(*rects, .{pos = #run xy(0.0,  0.0), halfsize = #run xy(30.0)});
+    array_add(*rects, .{pos = #run xy(40.0, 0.0), halfsize = #run xy(30.0)});
+
+    quit := false;
+    last_time := get_time();
+    panning: bool = false;
+    last_mouse_pos := mouse();
+    while !quit {
+        dt := cast(float)(get_time() - last_time);
+        last_time = get_time();
+        Input.update_window_events();
+        mouse_delta := mouse() - last_mouse_pos; // using Input.mouse_delta_x seems to incorrectly accumulate
+        last_mouse_pos = mouse();
+
+        for Input.get_window_resizes() {
+            Simp.update_window(it.window);  // Simp will do nothing if it doesn't care about this window.
+            
+            if it.window == window {
+                should_reinit := (it.width != window_width) || (it.height != window_height);
+
+                window_width  = it.width;
+                window_height = it.height;
+
+                //if should_reinit my_init_fonts();  // Resize the font for the new window size.
+            }
+        }
+
+        print("%\n", Input.mouse_delta_z);
+        camera.zoom *= 1.0 - 0.1*Input.mouse_delta_z/120.0;
+        if panning {
+            camera.pos -= mouse_delta;
+
+            //camera.pos -= xy(Input.mouse_delta_x, -Input.mouse_delta_y);
+            
+            // this doesn't fix it
+            //Input.mouse_delta_x = 0;
+            //Input.mouse_delta_y = 0;
+        }
+
+        rects[0].rotation += dt * 1.0;
+
+        Simp.clear_render_target(0.0, 0.0, 0.0, 1.0);
+
+        drawing_in_world_space = true;
+        for rects draw_rect(it);
+        line(xy(0.0, 0.0), screen_to_world(mouse()));
+        drawing_in_world_space = false;
+
+        Simp.swap_buffers(window);
+
+        for Input.events_this_frame {
+            if it.type == .QUIT then quit = true;
+
+            if it.type == {
+              case .KEYBOARD;
+                if it.key_pressed && it.key_code == .ESCAPE {
+                    quit = true;
+                }
+                if it.key_code == .MOUSE_BUTTON_LEFT {
+                    panning = cast(bool)it.key_pressed;
+                }
+            }
+        }
+
+    }
+}