Add sanity check on pixels_per_point range

epaint/src/text/fonts.rs

@@ -184,6 +184,12 @@ pub struct Fonts {
 
 impl Fonts {
     pub fn from_definitions(pixels_per_point: f32, definitions: FontDefinitions) -> Self {
+        assert!(
+            0.0 < pixels_per_point && pixels_per_point < 100.0,
+            "pixels_per_point out of range: {}",
+            pixels_per_point
+        );
+
         // We want an atlas big enough to be able to include all the Emojis in the `TextStyle::Heading`,
         // so we can show the Emoji picker demo window.
         let mut atlas = TextureAtlas::new(2048, 64);

epaint/src/texture_atlas.rs

@@ -82,7 +82,12 @@ impl TextureAtlas {
         /// On modern high-precision GPUs this is not needed.
         const PADDING: usize = 1;
 
-        assert!(w <= self.texture.width);
+        assert!(
+            w <= self.texture.width,
+            "Tried to allocate a {} wide glyph in a {} wide texture atlas",
+            w,
+            self.texture.width
+        );
         if self.cursor.0 + w > self.texture.width {
             // New row:
             self.cursor.0 = 0;