mod: change interface for rendering of Layouts and Widgets to use a non-const pointer to the renderer instead

src/widget.zig

@@ -1,7 +1,7 @@
 //! Dynamic dispatch for widget implementations.
 //! Each widget should at last implement these functions:
 //! - handle(this: *@This(), event: Event) ?Event {}
-//! - render(this: *@This(), renderer: Renderer) !void {}
+//! - render(this: *@This(), renderer: *Renderer) !void {}
 //! - deinit(this: *@This()) void {}
 //!
 //! Create a `Widget` using `createFrom(object: anytype)` and use them through
@@ -27,7 +27,7 @@ pub fn Widget(comptime Event: type, comptime Renderer: type) type {
 
         const VTable = struct {
             handle: *const fn (this: *WidgetType, event: Event) ?Event,
-            render: *const fn (this: *WidgetType, renderer: Renderer) anyerror!void,
+            render: *const fn (this: *WidgetType, renderer: *Renderer) anyerror!void,
             deinit: *const fn (this: *WidgetType) void,
         };
 
@@ -51,7 +51,7 @@ pub fn Widget(comptime Event: type, comptime Renderer: type) type {
         }
 
         // Render the content of this `Widget` given the `Size` of the widget (.resize System`Event`).
-        pub fn render(this: *WidgetType, renderer: Renderer) !void {
+        pub fn render(this: *WidgetType, renderer: *Renderer) !void {
             try this.vtable.render(this, renderer);
         }
 
@@ -73,7 +73,7 @@ pub fn Widget(comptime Event: type, comptime Renderer: type) type {
                     }.handle,
                     .render = struct {
                         // Return the entire content of this `Widget`.
-                        fn render(this: *WidgetType, renderer: Renderer) !void {
+                        fn render(this: *WidgetType, renderer: *Renderer) !void {
                             const widget: @TypeOf(object) = @ptrFromInt(this.object);
                             try widget.render(renderer);
                         }