Add Matthew's mandelbrot piece to title slide, and center everything.

src/slide/s1_title.rs

@@ -4,6 +4,8 @@ use crate::fade_in::fade_in;
 use crate::slide::Slide;
 use crate::{ctx_img, Margin};
 use eframe::egui::{Frame, TextureHandle, Ui, Vec2, Window};
+use eframe::emath::Pos2;
+use crate::window::WindowPosition;
 
 /// The first slide in the cartoon.
 #[derive(Default)]
@@ -37,29 +39,35 @@ impl Slide for Title {
 
     fn show(&mut self, ui: &mut Ui) {
         if self.examples.is_empty() {
-            // For now, these images are somewhat like placeholders.
             self.examples = vec![
                 ctx_img!(ui.ctx(), "abstract0.png"),
-                ctx_img!(ui.ctx(), "atom0.png"),
                 ctx_img!(ui.ctx(), "mud0_1.png"),
-                ctx_img!(ui.ctx(), "fluid0.png"),
-                ctx_img!(ui.ctx(), "raymarching1.png"),
-                ctx_img!(ui.ctx(), "atom2.png"),
+                ctx_img!(ui.ctx(), "raymarching0.png"),
                 ctx_img!(ui.ctx(), "raytracing0.png"),
-                ctx_img!(ui.ctx(), "rock0_1.png"),
                 ctx_img!(ui.ctx(), "atom1.png"),
-                ctx_img!(ui.ctx(), "abstract1.png"),
-                ctx_img!(ui.ctx(), "slime1.png"),
-                ctx_img!(ui.ctx(), "raymarching0.png"),
+                ctx_img!(ui.ctx(), "fluid0.png"),
                 ctx_img!(ui.ctx(), "slime0.png"),
                 ctx_img!(ui.ctx(), "line0.png"),
+                ctx_img!(ui.ctx(), "rock0_1.png"),
+                ctx_img!(ui.ctx(), "abstract1.png"),
+                ctx_img!(ui.ctx(), "slime1.png"),
+                ctx_img!(ui.ctx(), "atom2.png"),
+                ctx_img!(ui.ctx(), "raymarching1.png"),
+                ctx_img!(ui.ctx(), "mandelbrot.png"),
                 ctx_img!(ui.ctx(), "line1.png"),
             ];
         }
 
-        for example in &self.examples {
+        const COLUMNS: usize = 5;
+        const ROWS: usize = 3;
+        let available = ui.available_size();
+        for (i, example) in self.examples.iter().enumerate() {
+            let row = i / COLUMNS;
+            let column = i % COLUMNS;
+            let position = Pos2::new(column as f32 * available.y / ROWS as f32, row as f32 * available.y / ROWS as f32) + Vec2::new(62.0,16.0);
             Image::default()
-                .height(ui.available_height() * 0.295)
+                .height(available.y * 0.295)
+                .position(WindowPosition::Global(position))
                 .show(ui, example);
         }