Blender widgets for Dear ImGui

The Blender theme makes ImGui look like Blender. The Blender-widgets build makes it feel like Blender. Turn on one option and ImGui::SliderFloat becomes Blender’s number slider: drag it relative to where you pressed, hold Shift for precision, hold Ctrl to snap, click to type a value. Your ImGui code doesn’t change at all.

These aren’t look-alikes. BUI draws them with the same code as its own native widgets, a port of Blender’s interface_widgets.cc, and a test checks they’re the same pixels.

Look at the Vector row: three separate boxes on the left, one joined row on the right, the way Blender aligns X/Y/Z fields. The Slider has a fill bar instead of a grab handle, and the checkboxes and radio buttons are Blender’s.

Turn it on

cmake -S . -B build -DBUI_IMGUI_BLENDER_WIDGETS=ON

cmake -S . -B build -DBUI_IMGUI_BLENDER_WIDGETS=ON

[dependencies]
blenderui-imgui = { git = "https://github.com/ppmpreetham/BUI", features = ["blender-widgets"] }

When the build has them, they’re on by default. You can switch at runtime, for example to compare:

Switching off goes back to ImGui’s own drawing and interaction.

What feels different

If you know ImGui, these are the changes your hands will notice:

• Sliders don’t jump. A press doesn’t move the value; dragging changes it relative to where you pressed. A click without a drag lets you type a value. (ImGui jumps to the pointer on press.)
• Number fields (Drag*) type on click. A click without a drag types a value; ImGui needs Ctrl+click, a double-click or io.ConfigDragClickToInputText. The arrows at each end step the value. The drag starts after 0.25 widget units.
• Shift is slower, not faster. It’s Blender’s precision mode, 10× slower on number fields and 20× on sliders. (ImGui: Shift faster, Alt slower.) Ctrl snaps while you drag.
• Checkboxes toggle on press, and you can drag across several to give them all the same state. (ImGui toggles on release.)
• A quick second press is a new drag, not a double-click.
• Text fields put their text 0.4 widget units from the left edge, as Blender does.
• Menu check marks are Blender’s check box, in ImGui’s mark column (Blender puts the box on the left).

Logarithmic sliders and drags, reversed slider ranges, the keyboard and gamepads keep ImGui’s interaction, drawn as Blender widgets.

The mapping

Two layout details:

• “Label: value” formats. A number field or slider whose format contains a : (like "Width: %.0f", or ColorEdit’s "R:%3d") shows Blender’s way: label on the left, value on the right. Other formats are centred. ImGui’s own label argument stays outside, on the right, so layouts and label columns keep working.
• Joined rows. The components of DragFloat2/3/4, DragInt*, SliderFloat2/3/4, SliderInt*, Drag*Range2 and ColorEdit join into one rounded row, as Blender aligns vectors.

How it works

• A drop-in copy. blender/imgui_widgets_blender.cpp is a copy of ImGui’s imgui_widgets.cpp, and CMake compiles it instead of the original. Same functions, same ABI, so every binding gets Blender widgets with no change. Every edit in it is marked BUI:.
• ImGui’s logic is untouched. Items, IDs, layout, navigation and the text-editing engine are ImGui’s own. What changes is how each widget is drawn and, for number fields, sliders and checkboxes, how the mouse drives it.
• Drawn by the kit. Each widget becomes a draw-list callback. While rendering, the backend hands it to the kit’s BK_draw_widget, the same drawing BUI’s native widgets use, clipped as ImGui asked.
• Same pixels, proven. The test imgui_blender_widgets_match_kit renders nine kit widgets next to the same widgets through ImGui and requires them to match exactly at scale 1.
• Still idle when idle. The callback data is part of the backend’s change check, so “redraw only on change” still works, on the CPU and the GPU.

Gaps

Honest list. These keep ImGui’s behaviour or drawing for now:

• Blender’s vertical multi-value drag (drag down over fields, then sideways) and Alt (edit all linked fields) aren’t implemented. The cursor isn’t hidden and wrapped while you scrub. Coming soon
• Window title bars and frames, tooltips, BeginPopup and context-menu backgrounds, table headers keep ImGui’s rendering in the Blender style. Only combos and BeginMenu menus get Blender’s menu backdrop.
• ColorPicker3/4 keeps ImGui’s drawing: the Blender-widgets build doesn’t route it to Blender’s color picker yet. So do VSlider*, PlotLines, PlotHistogram, ImageButton, Bullet and TextLink.
• Text being typed uses ImGui’s glyphs, because ImGui measures its cursor and selection with them.
• An indeterminate ProgressBar (a negative fraction) shows the moving end of ImGui’s segment.

Next steps