[zgui] Fixed buffer type for inputText* to include null sentinel.

The slice length is for maximum text length, whereas the sentinel
denotes the current text length.

Added output of current text length, which would have errored before
this change since the buffers didn't include a sentinel in their type.

See https://github.com/zig-gamedev/zig-gamedev/issues/352#issuecomment-2038175998

libs/zgui/src/gui.zig

@@ -2333,7 +2333,7 @@ pub const InputTextCallbackData = extern struct {
 pub const InputTextCallback = *const fn (data: *InputTextCallbackData) i32;
 //--------------------------------------------------------------------------------------------------
 pub fn inputText(label: [:0]const u8, args: struct {
-    buf: []u8,
+    buf: [:0]u8,
     flags: InputTextFlags = .{},
     callback: ?InputTextCallback = null,
     user_data: ?*anyopaque = null,
@@ -2357,7 +2357,7 @@ extern fn zguiInputText(
 ) bool;
 //--------------------------------------------------------------------------------------------------
 pub fn inputTextMultiline(label: [:0]const u8, args: struct {
-    buf: []u8,
+    buf: [:0]u8,
     w: f32 = 0.0,
     h: f32 = 0.0,
     flags: InputTextFlags = .{},
@@ -2388,7 +2388,7 @@ extern fn zguiInputTextMultiline(
 //--------------------------------------------------------------------------------------------------
 pub fn inputTextWithHint(label: [:0]const u8, args: struct {
     hint: [:0]const u8,
-    buf: []u8,
+    buf: [:0]u8,
     flags: InputTextFlags = .{},
     callback: ?InputTextCallback = null,
     user_data: ?*anyopaque = null,

samples/gui_test_wgpu/src/gui_test_wgpu.zig

@@ -18,6 +18,9 @@ const DemoState = struct {
     font_normal: zgui.Font,
     font_large: zgui.Font,
     draw_list: zgui.DrawList,
+    alloced_input_text_buf: [:0]u8,
+    alloced_input_text_multiline_buf: [:0]u8,
+    alloced_input_text_with_hint_buf: [:0]u8,
 };
 var _te: *zgui.te.TestEngine = undefined;
 
@@ -105,7 +108,6 @@ fn create(allocator: std.mem.Allocator, window: *zglfw.Window) !*DemoState {
     const style = zgui.getStyle();
 
     style.window_min_size = .{ 320.0, 240.0 };
-    style.window_border_size = 8.0;
     style.scrollbar_size = 6.0;
     {
         var color = style.getColor(.scrollbar_grab);
@@ -133,7 +135,13 @@ fn create(allocator: std.mem.Allocator, window: *zglfw.Window) !*DemoState {
         .font_normal = font_normal,
         .font_large = font_large,
         .draw_list = draw_list,
+        .alloced_input_text_buf = try allocator.allocSentinel(u8, 128, 0),
+        .alloced_input_text_multiline_buf = try allocator.allocSentinel(u8, 128, 0),
+        .alloced_input_text_with_hint_buf = try allocator.allocSentinel(u8, 128, 0),
     };
+    demo.alloced_input_text_buf[0] = 0;
+    demo.alloced_input_text_multiline_buf[0] = 0;
+    demo.alloced_input_text_with_hint_buf[0] = 0;
 
     return demo;
 }
@@ -144,6 +152,9 @@ fn destroy(allocator: std.mem.Allocator, demo: *DemoState) void {
     zgui.destroyDrawList(demo.draw_list);
     zgui.deinit();
     demo.gctx.destroy(allocator);
+    allocator.free(demo.alloced_input_text_buf);
+    allocator.free(demo.alloced_input_text_multiline_buf);
+    allocator.free(demo.alloced_input_text_with_hint_buf);
     allocator.destroy(demo);
 }
 
@@ -463,9 +474,9 @@ fn update(demo: *DemoState) !void {
 
         if (zgui.collapsingHeader("Widgets: Input with Keyboard", .{})) {
             const static = struct {
-                var buf: [128]u8 = undefined;
-                var buf1: [128]u8 = undefined;
-                var buf2: [128]u8 = undefined;
+                var input_text_buf = [_:0]u8{0} ** 128;
+                var input_text_multiline_buf = [_:0]u8{0} ** 128;
+                var input_text_with_hint_buf = [_:0]u8{0} ** 128;
                 var v1: f32 = 0;
                 var v2: [2]f32 = .{ 0, 0 };
                 var v3: [3]f32 = .{ 0, 0, 0 };
@@ -478,12 +489,30 @@ fn update(demo: *DemoState) !void {
                 var si8: i8 = 0;
                 var v3u8: [3]u8 = .{ 0, 0, 0 };
             };
-            _ = zgui.inputText("Input text", .{ .buf = static.buf[0..] });
-            _ = zgui.inputTextMultiline("Input text multiline", .{ .buf = static.buf1[0..] });
-            _ = zgui.inputTextWithHint(
-                "Input text with hint",
-                .{ .hint = "Enter your name", .buf = static.buf2[0..] },
-            );
+            zgui.separatorText("static input text");
+            _ = zgui.inputText("Input text", .{ .buf = static.input_text_buf[0..] });
+            _ = zgui.text("length of Input text {}", .{std.mem.len(@as([*:0]u8, static.input_text_buf[0..]))});
+
+            _ = zgui.inputTextMultiline("Input text multiline", .{ .buf = static.input_text_multiline_buf[0..] });
+            _ = zgui.text("length of Input text multiline {}", .{std.mem.len(@as([*:0]u8, static.input_text_multiline_buf[0..]))});
+            _ = zgui.inputTextWithHint("Input text with hint", .{
+                .hint = "Enter your name",
+                .buf = static.input_text_with_hint_buf[0..],
+            });
+            _ = zgui.text("length of Input text with hint {}", .{std.mem.len(@as([*:0]u8, static.input_text_with_hint_buf[0..]))});
+
+            zgui.separatorText("alloced input text");
+            _ = zgui.inputText("Input text alloced", .{ .buf = demo.alloced_input_text_buf });
+            _ = zgui.text("length of Input text alloced {}", .{std.mem.len(demo.alloced_input_text_buf.ptr)});
+            _ = zgui.inputTextMultiline("Input text multiline alloced", .{ .buf = demo.alloced_input_text_multiline_buf });
+            _ = zgui.text("length of Input text multiline {}", .{std.mem.len(demo.alloced_input_text_multiline_buf.ptr)});
+            _ = zgui.inputTextWithHint("Input text with hint alloced", .{
+                .hint = "Enter your name",
+                .buf = demo.alloced_input_text_with_hint_buf,
+            });
+            _ = zgui.text("length of Input text with hint alloced {}", .{std.mem.len(demo.alloced_input_text_with_hint_buf.ptr)});
+
+            zgui.separatorText("input numeric");
             _ = zgui.inputFloat("Input float 1", .{ .v = &static.v1 });
             _ = zgui.inputFloat2("Input float 2", .{ .v = &static.v2 });
             _ = zgui.inputFloat3("Input float 3", .{ .v = &static.v3 });