terminal: updating render state with tests

src/terminal/render.zig

@@ -42,7 +42,7 @@ pub const RenderState = struct {
     /// area and scrolling with new output.
     viewport_is_bottom: bool,
 
-    /// The rows (y=0 is top) of the viewport.
+    /// The rows (y=0 is top) of the viewport. Guaranteed to be `rows` length.
     ///
     /// This is a MultiArrayList because only the update cares about
     /// the allocators. Callers care about all the other properties, and
@@ -75,7 +75,7 @@ pub const RenderState = struct {
         /// Arena used for any heap allocations for this row,
         arena: ArenaAllocator.State,
 
-        /// The cells in this row, always `cols` length.
+        /// The cells in this row. Guaranteed to be `cols` length.
         cells: std.MultiArrayList(Cell),
 
         /// A dirty flag that can be used by the renderer to track
@@ -113,7 +113,8 @@ pub const RenderState = struct {
         alloc: Allocator,
         t: *Terminal,
     ) Allocator.Error!void {
-        self.redraw = redraw: {
+        const s: *Screen = t.screens.active;
+        const redraw = redraw: {
             // If our screen key changed, we need to do a full rebuild
             // because our render state is viewport-specific.
             if (t.screens.active_key != self.screen) break :redraw true;
@@ -134,17 +135,23 @@ pub const RenderState = struct {
                 if (v > 0) break :redraw true;
             }
 
+            // If our dimensions changed, we do a full rebuild.
+            if (self.rows != s.pages.rows or
+                self.cols != s.pages.cols)
+            {
+                break :redraw true;
+            }
+
             break :redraw false;
         };
 
         // Full redraw resets our state completely.
-        if (self.redraw) {
+        if (redraw) {
             self.* = .empty;
             self.screen = t.screens.active_key;
+            self.redraw = true;
         }
 
-        const s: *Screen = t.screens.active;
-
         // Always set our cheap fields, its more expensive to compare
         self.rows = s.pages.rows;
         self.cols = s.pages.cols;
@@ -186,7 +193,7 @@ pub const RenderState = struct {
         var y: size.CellCountInt = 0;
         while (row_it.next()) |row_pin| : (y = y + 1) {
             // If the row isn't dirty then we assume it is unchanged.
-            if (!self.redraw and !row_pin.isDirty()) continue;
+            if (!redraw and !row_pin.isDirty()) continue;
 
             // Promote our arena. State is copied by value so we need to
             // restore it on all exit paths so we don't leak memory.
@@ -306,3 +313,32 @@ test {
     defer state.deinit(alloc);
     try state.update(alloc, &t);
 }
+
+test "basic text" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var t = try Terminal.init(alloc, .{
+        .cols = 10,
+        .rows = 3,
+    });
+    defer t.deinit(alloc);
+
+    var s = t.vtStream();
+    defer s.deinit();
+    try s.nextSlice("ABCD");
+
+    var state: RenderState = .empty;
+    defer state.deinit(alloc);
+    try state.update(alloc, &t);
+
+    // Verify we have the right number of rows
+    const row_data = state.row_data.slice();
+    try testing.expectEqual(3, row_data.len);
+
+    // All rows should have cols cells
+    const cells = row_data.items(.cells);
+    try testing.expectEqual(10, cells[0].len);
+    try testing.expectEqual(10, cells[1].len);
+    try testing.expectEqual(10, cells[2].len);
+}