Expose some missing ImPlot functions by odorovskoy · Pull Request #98 · zig-gamedev/zgui

odorovskoy · 2026-02-23T11:54:09Z

Changes for #97.

Copilot

Pull request overview

This pull request exposes additional ImPlot functions in the zgui library, addressing issue #97. The changes add Zig wrappers and C++ bindings for various ImPlot functions related to styling, axis configuration, coordinate transformation, subplots, and custom item rendering. The implementation follows existing patterns in the codebase for wrapping C++ ImPlot APIs with idiomatic Zig interfaces.

Changes:

Added C++ wrapper functions in zplot.cpp for new ImPlot functions including style setters, axis configuration, coordinate conversions, and internal functions for custom item rendering
Implemented Zig API bindings in plot.zig with struct-based optional parameters following existing conventions
Added AxisOrAuto enum to support IMPLOT_AUTO (-1) sentinel value for axis parameters
Updated StyleCol enum to include auto = -1 for IMPLOT_AUTO color support
Added default parameter to addLine in gui.zig for consistency with other drawing functions
Updated .gitignore to exclude IDE folders

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 6 comments.

File	Description
src/zplot.cpp	Added C++ wrappers for SetNextLineStyle, SetNextFillStyle, SetNextMarkerStyle, SetNextErrorBarStyle, SetupAxisFormat, SetupAxisTicks, SetupAxisLimitsConstraints, SetupAxisZoomConstraints, SetNextAxesToFit, PixelsToPlot, PlotToPixels, GetPlotPos, GetPlotSize, GetPlotMousePos, BeginSubplots, EndSubplots, PushPlotClipRect, PopPlotClipRect, BeginItem, EndItem, and FitPoint functions. Includes implot_internal.h for BeginItem/EndItem.
src/plot.zig	Added Zig bindings for all new C++ wrappers with idiomatic struct-based APIs. Modified StyleCol and Axis enums to use i32 and added AxisOrAuto enum. Included formatter wrapper function for setupAxisFormat.
src/gui.zig	Added default value (1.0) to thickness parameter in addLine function for consistency with other drawing functions.
.gitignore	Added patterns to ignore IDE folders (.vscode and .idea).

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Copilot · 2026-02-25T20:32:53Z

src/plot.zig

+pub const StyleCol = enum(i32) {
+    auto = -1,
+    line = 0,


Adding auto = -1 to the StyleCol enum will break the array size calculation in line 84 of the Style struct. The enum now has 22 fields (including auto), but the C++ ImPlotStyle.Colors array has size ImPlotCol_COUNT which is 21. The auto value is a sentinel (like IMPLOT_AUTO) and should not be counted as an array index. This will cause a size mismatch with the C++ struct and potential memory corruption.

True. In general, zgui Style itself is an extern struct while ImGuiStyle is not, it's a C++ struct. Strictly speaking #65 should be completed to use extern structs with the same layout on both sides.

Copilot · 2026-02-25T20:32:53Z

src/plot.zig


+//----------------------------------------------------------------------------------------------
+/// Get the plot draw list for custom rendering to the current plot area. Call between begin/endPlot.
+pub const getPlotDrawList = gui.getWindowDrawList;


The alias to gui.getWindowDrawList is incorrect. ImPlot's GetPlotDrawList() is a separate function that should have its own C++ wrapper in zplot.cpp and Zig binding. While both return ImDrawList*, they serve different purposes - GetPlotDrawList() returns the draw list for the current plot area, while GetWindowDrawList() returns the draw list for the current window. Without a proper wrapper function zguiPlot_GetPlotDrawList in zplot.cpp, this will not work.

Suggested change

pub const getPlotDrawList = gui.getWindowDrawList;

const GetWindowDrawListFn = @TypeOf(gui.getWindowDrawList);

const GetWindowDrawListReturnType = @typeInfo(GetWindowDrawListFn).Fn.return_type.?;

pub fn getPlotDrawList() GetWindowDrawListReturnType {

return zguiPlot_GetPlotDrawList();

}

extern fn zguiPlot_GetPlotDrawList() GetWindowDrawListReturnType;

Well, I don't think there is a dedicated plot draw list, that's why it works perfectly fine as is, without any wrappers, because ImPlot just returns ImGui window draw list. I'll create the wrapper function though, to hide that implementation detail.

Copilot · 2026-02-25T20:32:53Z

src/plot.zig

+    labels: [][*:0]const u8 = &.{},
+    keep_default: bool = false,
+};
+pub fn setupAxisTicks(axis: Axis, args: SetupAxisTicks) void {
+    const n_ticks = std.math.cast(i32, args.values.len) orelse {
+        @panic("Too many tick values!");
+    };
+    zguiPlot_SetupAxisTicks(axis, args.values.ptr, n_ticks, args.labels.ptr, args.keep_default);
+}
+extern fn zguiPlot_SetupAxisTicks(
+    axis: Axis,
+    values: [*]const f64,
+    n_ticks: i32,
+    labels: [*][*:0]const u8,


The default for args.labels in SetupAxisTicks is an empty slice (&.{}), but setupAxisTicks always passes args.labels.ptr along with n_ticks = args.values.len to zguiPlot_SetupAxisTicks. The underlying ImPlot API expects either a null pointer or an array of at least n_ticks label pointers; passing a non-null pointer to a zero-length buffer can cause out-of-bounds reads when ImPlot indexes labels, potentially leaking or corrupting memory when it interprets arbitrary memory as strings. Make labels optional and pass a null pointer when no labels are provided, or ensure the labels buffer has at least n_ticks elements and validate labels.len against values.len before calling into ImPlot.

Suggested change

labels: [][*:0]const u8 = &.{},

keep_default: bool = false,

};

pub fn setupAxisTicks(axis: Axis, args: SetupAxisTicks) void {

const n_ticks = std.math.cast(i32, args.values.len) orelse {

@panic("Too many tick values!");

};

zguiPlot_SetupAxisTicks(axis, args.values.ptr, n_ticks, args.labels.ptr, args.keep_default);

}

extern fn zguiPlot_SetupAxisTicks(

axis: Axis,

values: [*]const f64,

n_ticks: i32,

labels: [*][*:0]const u8,

/// Optional tick labels. If null, no labels are provided and a null pointer is passed to ImPlot.

/// If non-null, the slice must have at least `values.len` elements.

labels: ?[][*:0]const u8 = null,

keep_default: bool = false,

};

pub fn setupAxisTicks(axis: Axis, args: SetupAxisTicks) void {

const n_ticks = std.math.cast(i32, args.values.len) orelse {

@panic("Too many tick values!");

};

const labels_ptr: ?[*][*:0]const u8 = blk: {

if (args.labels) |labels_slice| {

if (labels_slice.len < args.values.len) {

@panic("Number of labels must be at least the number of tick values!");

}

break :blk labels_slice.ptr;

} else {

break :blk null;

}

};

zguiPlot_SetupAxisTicks(axis, args.values.ptr, n_ticks, labels_ptr, args.keep_default);

}

extern fn zguiPlot_SetupAxisTicks(

axis: Axis,

values: [*]const f64,

n_ticks: i32,

labels: ?[*][*:0]const u8,

Good catch, I'll push updates shortly.

Copilot

Pull request overview

Copilot reviewed 3 out of 4 changed files in this pull request and generated 5 comments.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Copilot · 2026-03-05T23:45:04Z

src/plot.zig

+pub fn beginSubplots(title_id: [*:0]const u8, args: BeginSubplots) bool {
+    // Both must be greater than 0 according to ImPlot docs.
+    const rs: i32 = @intCast(args.rows);
+    const cs: i32 = @intCast(args.cols);
+    return zguiPlot_BeginSubplots(title_id, rs, cs, args.width, args.height, args.flags, args.row_ratios, args.col_ratios);
+}


beginSubplots accepts title_id: [*:0]const u8 whereas beginPlot uses [:0]const u8. Taking the raw pointer here makes it easier to accidentally pass a non-null-terminated string and is inconsistent with the rest of the public API. Consider changing the parameter to [:0]const u8 for safety and consistency (the extern wrapper can still take [ *:0 ]const u8).

Copilot · 2026-03-05T23:45:04Z

src/plot.zig

+    const rs: i32 = @intCast(args.rows);
+    const cs: i32 = @intCast(args.cols);


beginSubplots comments that rows/cols must be > 0, but it doesn't enforce this (0 is still representable in u32). Passing 0 through to ImPlot can trigger assertions or undefined behavior depending on build settings. Add a runtime check (assert/panic) for args.rows > 0 and args.cols > 0, and consider using std.math.cast(i32, ...) to produce a clearer error if the values don't fit in i32.

Suggested change

const rs: i32 = @intCast(args.rows);

const cs: i32 = @intCast(args.cols);

assert(args.rows > 0);

assert(args.cols > 0);

const rs = std.math.cast(i32, args.rows) orelse @panic("BeginSubplots: rows value does not fit into i32");

const cs = std.math.cast(i32, args.cols) orelse @panic("BeginSubplots: cols value does not fit into i32");

src/zplot.cpp

src/plot.zig

Copilot · 2026-03-05T23:45:05Z

src/plot.zig

+pub fn setupAxisTicks(axis: Axis, args: SetupAxisTicks) void {
+    const n_ticks = std.math.cast(i32, args.values.len) orelse {
+        @panic("Too many tick values!");
+    };
+
+    const labels_ptr = blk: {
+        if (args.labels) |labels| {
+            break :blk if (labels.len != 0) labels.ptr else null;
+        } else {
+            break :blk null;
+        }
+    };
+
+    zguiPlot_SetupAxisTicks(axis, args.values.ptr, n_ticks, labels_ptr, args.keep_default);


setupAxisTicks can pass a labels buffer that is shorter than args.values.len to zguiPlot_SetupAxisTicks without any validation. If callers supply args.labels where labels.len is non-zero but less than args.values.len, ImPlot will index past the end of the labels array and treat arbitrary memory as label pointers, which can leak memory contents or corrupt process state. Consider enforcing that labels is null or has at least args.values.len elements before calling zguiPlot_SetupAxisTicks, and panic or return early when this precondition is not met.

…nctions

hazeycode

Thanks!

odorovskoy added 2 commits February 23, 2026 14:26

Expose some missing ImPlot functions

d35b4e1

Expose ImPlot::SetNext*Style functions

0425d4c

hazeycode requested a review from Copilot February 25, 2026 20:24

Copilot started reviewing on behalf of hazeycode February 25, 2026 20:25 View session

Copilot AI reviewed Feb 25, 2026

View reviewed changes

zig-gamedev deleted a comment from Copilot AI Feb 25, 2026

Expose some missing ImPlot methods (review updates)

f6364d1

hazeycode requested a review from Copilot March 5, 2026 23:38

Copilot started reviewing on behalf of hazeycode March 5, 2026 23:38 View session

Copilot AI reviewed Mar 5, 2026

View reviewed changes

odorovskoy added 2 commits March 7, 2026 18:34

Merge remote-tracking branch 'origin/main' into feat/expose-implot-fu…

9f6c1fc

…nctions

Expose some missing ImPlot methods (more review updates)

ecd6cad

hazeycode approved these changes Mar 8, 2026

View reviewed changes

hazeycode merged commit 1af65a8 into zig-gamedev:main Mar 8, 2026
3 checks passed

odorovskoy deleted the feat/expose-implot-functions branch March 9, 2026 06:23

-pub const getPlotDrawList = gui.getWindowDrawList;
+const GetWindowDrawListFn = @TypeOf(gui.getWindowDrawList);
+const GetWindowDrawListReturnType = @typeInfo(GetWindowDrawListFn).Fn.return_type.?;
+pub fn getPlotDrawList() GetWindowDrawListReturnType {
+    return zguiPlot_GetPlotDrawList();
+}
+extern fn zguiPlot_GetPlotDrawList() GetWindowDrawListReturnType;

		const rs: i32 = @intCast(args.rows);
		const cs: i32 = @intCast(args.cols);

-    const rs: i32 = @intCast(args.rows);
-    const cs: i32 = @intCast(args.cols);
+    assert(args.rows > 0);
+    assert(args.cols > 0);
+    const rs = std.math.cast(i32, args.rows) orelse @panic("BeginSubplots: rows value does not fit into i32");
+    const cs = std.math.cast(i32, args.cols) orelse @panic("BeginSubplots: cols value does not fit into i32");

Conversation

odorovskoy commented Feb 23, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Copilot AI Feb 25, 2026

Choose a reason for hiding this comment

Uh oh!

odorovskoy Feb 26, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 25, 2026

Choose a reason for hiding this comment

Uh oh!

odorovskoy Feb 26, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 25, 2026

Choose a reason for hiding this comment

Uh oh!

odorovskoy Feb 26, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Copilot AI Mar 5, 2026

Choose a reason for hiding this comment

Uh oh!

odorovskoy Mar 7, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Mar 5, 2026

Choose a reason for hiding this comment

Uh oh!

odorovskoy Mar 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Copilot AI Mar 5, 2026

Choose a reason for hiding this comment

Uh oh!

odorovskoy Mar 7, 2026

Choose a reason for hiding this comment

Uh oh!

hazeycode left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

odorovskoy Mar 7, 2026 •

edited

Loading