fix: sdl panics on empty string drawing

2 files changed, 17 insertions, 14 deletions

diff --git a/src/app.rs b/src/app.rs
index eef896d..ffa73dd 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -4,12 +4,12 @@ use crate::{
     command::CommandBox,
     consts::{colors::*, FONT_PATH},
     dither,
-    lisp::{error::LispError, eval, lex::Lexer, parse::Parser, prelude, EnvList},
+    lisp::{eval, lex::Lexer, parse::Parser, prelude, EnvList},
     message::Message,
     rect,
     symmetry::Symmetry,
     undo::{ModifyRecord, OpKind, PaintRecord, UndoStack},
-    utils::{draw_text, is_copy_event, is_paste_event},
+    utils::{draw_text, handle_error, is_copy_event, is_paste_event},
 };
 
 use std::{convert::From, fs::File, io::prelude::*, path::Path};
@@ -284,7 +284,7 @@ impl<'ctx, 'file> AppState<'ctx, 'file> {
                 Ok(val) => self.message.set_info(format!("{}", val)),
                 Err(eval_err) => self.message.set_error(format!("{}", eval_err)),
             },
-            Err(err) => self.message = AppState::handle_error(err, &lisp_expr),
+            Err(err) => self.message = handle_error(err, &lisp_expr),
         }
         self.command_box.hist_append();
 
@@ -292,15 +292,6 @@ impl<'ctx, 'file> AppState<'ctx, 'file> {
         self.mode = Mode::Draw;
     }
 
-    fn handle_error(err: LispError, src: &str) -> Message {
-        let mut message = Message::new();
-        match err {
-            LispError::Parse(p) => message.set_error(p.display(&src)),
-            eval_err => message.set_error(eval_err.to_string()),
-        }
-        message
-    }
-
     fn draw_grid(&mut self) {
         let cs = self.zoom as u32;
         let (width, height) = (self.width(), self.height());
diff --git a/src/utils.rs b/src/utils.rs
index 902f939..3e5ff55 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -1,4 +1,4 @@
-use crate::consts::FONT_PATH;
+use crate::{consts::FONT_PATH, lisp::error::LispError, message::Message};
 use sdl2::{
     keyboard::{Keycode, Mod},
     pixels::Color,
@@ -26,7 +26,10 @@ pub fn draw_text<S: AsRef<str>>(
     let mut font = ttf_context.load_font(FONT_PATH, 17).unwrap();
     font.set_style(sdl2::ttf::FontStyle::NORMAL);
     font.set_hinting(sdl2::ttf::Hinting::Mono);
-    let surface = font.render(text.as_ref()).blended(color).unwrap();
+    let surface = font
+        .render(if text.is_empty() { " " } else { text.as_ref() })
+        .blended(color)
+        .unwrap();
     let texture = texture_creator
         .create_texture_from_surface(&surface)
         .unwrap();
@@ -43,3 +46,12 @@ pub fn is_copy_event(keycode: Option<Keycode>, keymod: Mod) -> bool {
 pub fn is_paste_event(keycode: Option<Keycode>, keymod: Mod) -> bool {
     keycode == Some(Keycode::V) && (keymod == Mod::LCTRLMOD || keymod == Mod::RCTRLMOD)
 }
+
+pub fn handle_error(err: LispError, src: &str) -> Message {
+    let mut message = Message::new();
+    match err {
+        LispError::Parse(p) => message.set_error(p.display(&src)),
+        eval_err => message.set_error(eval_err.to_string()),
+    }
+    message
+}