font/coretext: creation functions can return null, handle OOM (#13679)

Catch NULL results from CoreFoundation/CoreText creation functions and
return error.OOM rather than null derefs later. I verified that this is
possible but didn't verify the behavior when it happens, this is just
defensive based on the report here: #13671 because it costs us nothing
really.

pkg/macos/foundation/string.zig

@@ -21,13 +21,13 @@ pub const String = opaque {
 
     pub fn createWithCharactersNoCopy(
         unichars: []const u16,
-    ) *String {
-        return @as(*String, @ptrFromInt(@intFromPtr(c.CFStringCreateWithCharactersNoCopy(
+    ) Allocator.Error!*String {
+        return @ptrCast(@constCast(c.CFStringCreateWithCharactersNoCopy(
             null,
             @ptrCast(unichars.ptr),
             @intCast(unichars.len),
             foundation.c.kCFAllocatorNull,
-        ))));
+        ) orelse return error.OutOfMemory));
     }
 
     pub fn release(self: *String) void {

pkg/macos/text/typesetter.zig

@@ -27,10 +27,10 @@ pub const Typesetter = opaque {
     pub fn createLine(
         self: *Typesetter,
         range: foundation.c.CFRange,
-    ) *text.Line {
-        return @ptrFromInt(@intFromPtr(c.CTTypesetterCreateLine(
+    ) Allocator.Error!*text.Line {
+        return @ptrCast(@constCast(c.CTTypesetterCreateLine(
             @ptrCast(self),
             range,
-        )));
+        ) orelse return error.OutOfMemory));
     }
 };

src/font/shaper/coretext.zig

@@ -361,7 +361,7 @@ pub const Shaper = struct {
         // Make room for the attributed string, CTTypesetter, and CTLine.
         try self.cf_release_pool.ensureUnusedCapacity(self.alloc, 4);
 
-        const str = macos.foundation.String.createWithCharactersNoCopy(state.unichars.items);
+        const str = try macos.foundation.String.createWithCharactersNoCopy(state.unichars.items);
         self.cf_release_pool.appendAssumeCapacity(str);
 
         // Create an attributed string from our string
@@ -381,7 +381,7 @@ pub const Shaper = struct {
         self.cf_release_pool.appendAssumeCapacity(typesetter);
 
         // Create a line from the typesetter
-        const line = typesetter.createLine(.{ .location = 0, .length = 0 });
+        const line = try typesetter.createLine(.{ .location = 0, .length = 0 });
         self.cf_release_pool.appendAssumeCapacity(line);
 
         // This keeps track of the current x offset (sum of advance.width) and

src/renderer/generic.zig

@@ -1146,6 +1146,11 @@ pub fn Renderer(comptime GraphicsAPI: type) type {
             state: *renderer.State,
             cursor_blink_visible: bool,
         ) Allocator.Error!void {
+            // CoreText shaping accumulates objects for deferred release over
+            // the course of a frame. Always flush those objects, including
+            // when rebuilding the frame fails due to memory pressure.
+            defer self.font_shaper.endFrame();
+
             // We fully deinit and reset the terminal state every so often
             // so that a particularly large terminal state doesn't cause
             // the renderer to hold on to retained memory.
@@ -1444,10 +1449,6 @@ pub fn Renderer(comptime GraphicsAPI: type) type {
                 // Update custom shader uniforms that depend on terminal state.
                 self.updateCustomShaderUniformsFromState();
             }
-
-            // Notify our shaper we're done for the frame. For some shapers,
-            // such as CoreText, this triggers off-thread cleanup logic.
-            self.font_shaper.endFrame();
         }
 
         /// Draw the frame to the screen.