Handle scroll in TextBuffer

src/buffer.rs

@@ -1,4 +1,7 @@
-use std::time::Instant;
+use std::{
+    cmp,
+    time::Instant,
+};
 
 use crate::{FontLayoutLine, FontLineIndex, FontMatches, FontShapeLine};
 
@@ -9,6 +12,8 @@ pub enum TextAction {
     Down,
     Backspace,
     Delete,
+    PageUp,
+    PageDown,
     Insert(char),
 }
 
@@ -30,13 +35,23 @@ pub struct TextBuffer<'a> {
     shape_lines: Vec<FontShapeLine<'a>>,
     layout_lines: Vec<FontLayoutLine<'a>>,
     font_size: i32,
-    line_width: i32,
+    line_height: i32,
+    width: i32,
+    height: i32,
     pub cursor: TextCursor,
     pub redraw: bool,
+    pub scroll: i32,
 }
 
 impl<'a> TextBuffer<'a> {
-    pub fn new(font_matches: &'a FontMatches<'a>, text: &str, font_size: i32, line_width: i32) -> Self {
+    pub fn new(
+        font_matches: &'a FontMatches<'a>,
+        text: &str,
+        font_size: i32,
+        line_height: i32,
+        width: i32,
+        height: i32,
+    ) -> Self {
         let mut text_lines: Vec<String> = text.lines().map(String::from).collect();
         if text_lines.is_empty() {
             text_lines.push(String::new());
@@ -47,9 +62,12 @@ impl<'a> TextBuffer<'a> {
             shape_lines: Vec::new(),
             layout_lines: Vec::new(),
             font_size,
-            line_width,
+            line_height,
+            width,
+            height,
             cursor: TextCursor::default(),
             redraw: false,
+            scroll: 0,
         }
     }
 
@@ -71,6 +89,21 @@ impl<'a> TextBuffer<'a> {
         }
     }
 
+    pub fn shape_until_scroll(&mut self) {
+        let lines = self.height / self.line_height;
+
+        let scroll_end = self.scroll + lines;
+        self.shape_until(scroll_end);
+
+        self.scroll = cmp::max(
+            0,
+            cmp::min(
+                self.layout_lines().len() as i32 - (lines - 1),
+                self.scroll,
+            ),
+        );
+    }
+
     pub fn reshape_line(&mut self, line_i: FontLineIndex) {
         let instant = Instant::now();
 
@@ -97,7 +130,7 @@ impl<'a> TextBuffer<'a> {
             let layout_i = self.layout_lines.len();
             line.layout(
                 self.font_size,
-                self.line_width,
+                self.width,
                 &mut self.layout_lines,
                 layout_i,
             );
@@ -131,7 +164,7 @@ impl<'a> TextBuffer<'a> {
         let shape_line = &self.shape_lines[line_i.get()];
         shape_line.layout(
             self.font_size,
-            self.line_width,
+            self.width,
             &mut self.layout_lines,
             insert_i,
         );
@@ -150,18 +183,40 @@ impl<'a> TextBuffer<'a> {
         self.font_size
     }
 
-    pub fn set_font_size(&mut self, font_size: i32) {
-        self.font_size = font_size;
-        self.relayout();
+    pub fn line_height(&self) -> i32 {
+        self.line_height
     }
 
-    pub fn line_width(&self) -> i32 {
-        self.line_width
+    pub fn set_font_metrics(&mut self, font_size: i32, line_height: i32) {
+        if font_size != self.font_size {
+            self.font_size = font_size;
+            self.relayout();
+        }
+
+        if line_height != self.line_height {
+            self.line_height = line_height;
+            self.shape_until_scroll();
+        }
     }
 
-    pub fn set_line_width(&mut self, line_width: i32) {
-        self.line_width = line_width;
-        self.relayout();
+    pub fn width(&self) -> i32 {
+        self.width
+    }
+
+    pub fn height(&self) -> i32 {
+        self.height
+    }
+
+    pub fn set_size(&mut self, width: i32, height: i32) {
+        if width != self.width {
+            self.width = width;
+            self.relayout();
+        }
+
+        if height != self.height {
+            self.height = height;
+            self.shape_until_scroll();
+        }
     }
 
     pub fn layout_lines(&self) -> &[FontLayoutLine] {
@@ -184,7 +239,7 @@ impl<'a> TextBuffer<'a> {
                     self.cursor.glyph -= 1;
                     self.redraw = true;
                 }
-            }
+            },
             TextAction::Right => {
                 let line = &self.layout_lines[self.cursor.line];
                 if self.cursor.glyph > line.glyphs.len() {
@@ -195,19 +250,19 @@ impl<'a> TextBuffer<'a> {
                     self.cursor.glyph += 1;
                     self.redraw = true;
                 }
-            }
+            },
             TextAction::Up => {
                 if self.cursor.line > 0 {
                     self.cursor.line -= 1;
                     self.redraw = true;
                 }
-            }
+            },
             TextAction::Down => {
                 if self.cursor.line + 1 < self.layout_lines.len() {
                     self.cursor.line += 1;
                     self.redraw = true;
                 }
-            }
+            },
             TextAction::Backspace => {
                 let line = &self.layout_lines[self.cursor.line];
                 if self.cursor.glyph > line.glyphs.len() {
@@ -221,7 +276,7 @@ impl<'a> TextBuffer<'a> {
                     text_line.remove(glyph.start);
                     self.reshape_line(line.line_i);
                 }
-            }
+            },
             TextAction::Delete => {
                 let line = &self.layout_lines[self.cursor.line];
                 if self.cursor.glyph < line.glyphs.len() {
@@ -230,7 +285,19 @@ impl<'a> TextBuffer<'a> {
                     text_line.remove(glyph.start);
                     self.reshape_line(line.line_i);
                 }
-            }
+            },
+            TextAction::PageUp => {
+                let lines = self.height / self.line_height;
+                self.scroll -= lines;
+                self.redraw = true;
+                self.shape_until_scroll();
+            },
+            TextAction::PageDown => {
+                let lines = self.height / self.line_height;
+                self.scroll += lines;
+                self.redraw = true;
+                self.shape_until_scroll();
+            },
             TextAction::Insert(character) => {
                 let line = &self.layout_lines[self.cursor.line];
                 if self.cursor.glyph >= line.glyphs.len() {
@@ -255,7 +322,7 @@ impl<'a> TextBuffer<'a> {
                     self.cursor.glyph += 1;
                     self.reshape_line(line.line_i);
                 }
-            }
+            },
         }
     }
 }