RmlUi 6.1

The Easter bunny is here with a treat, a new release! Following up on one of the largest releases yet, the newly minted RmlUi 6.1 brings what has amassed to a great number of quality-of-life improvements, and some bug fixes too. Overall, the quality of the library should feel more polished. Please see the changelog below for all the goodies. As usual, the documentation has been updated and should reflect the new changes. Make sure to check the breaking changes before upgrading, although most users should not be significantly impacted.

We continue to see an influx of new users and contributors, which is always great to see! The community continues to thrive, and there are a lot of nice and skilled people helping to make this library better for everyone. I want to give a big thanks to every one of you. It's also a nice validation to see RmlUi being used in more commercial endeavors recently, two of which being Killing Time: Resurrected and The Thing: Remastered. See also the continuously updated list of thirdparty integrations and resources, and let me know if you have something to add here.

With more users and activity, the backlog of issues and pull requests has also grown a bit over the last year or so. I have been making an extra effort lately at getting through many of them, although some have been stuck longer than I'd like. I hope for some understanding, my time and resources are after all limited. Certain issues or requests are also more complicated, or require more research to understand their trade-offs.

In addition to the contributors listed in the changelog, I also want to specially mention contributors to the documentation: @AmaiKinono and @viseztrance. Good documentation is just as important as new features, so thank you for helping out with that! I also want to mention @mwl4, @dmikushin, and @gleblebedev, for some great initiatives and pull requests that ultimately didn't end up being merged directly. Those contributions are just as valuable, and many of the features did end up being integrated into the library in some shape, so make sure to keep the ideas and contributions coming!

Have fun with the library, and feel free to post your creations on the gitter chat or in the discussions.

RmlUi 6.1 changelog

Prevent single pixel gaps between elements

This release addresses the issue of 1px gaps appearing between fractionally sized elements when placed border-to-border. This was particularly pronounced in DPI-scaled layouts, as that often leads to fractionally sized elements.

The solution involves rounding the rendered size of elements based on their absolute positions to ensure that the bottom/right of one element matches the top/left of the next element. This implies that the rendered size of a fractional element may vary by up to one pixel. This generally matches how web browsers behave. Floating-point precision issues may still cause rare gaps, but the improvements should cover almost all cases. See the commit message for details. Resolves #438, thanks to @mwl4 for the extensive initiative and proof of concept.

In particular, this fixes several situations with single pixel gaps and overlaps:

• Gap of 1px between border or backgrounds of neighboring elements.
• Overlap of 1px between border or backgrounds of neighboring elements.
• Table cell backgrounds overlap the table border by 1px.
• Gap between nested elements in a flex container.
• Clipping area offset by 1px compared to the border area.

Handle element

The <handle> element has received several major improvements.

• The handle now retains the anchoring that applies to the target element, even after moving or sizing it. #637
  • If an element has all of its inset (top/right/bottom/left) properties set, this determines the size, and anchors to all edges. Previously, we would break the anchoring and just declare its new position or size. Now, positioning and sizing is performed in a way that retains this anchoring. Similarly, this applies to every combination of anchoring.
  • Thus, when first sizing and moving the target and then resizing its container, the element can now still resize itself to match the new dimensions.
• The edge_margin attribute is introduced to constrain the target placement to the edges of its containing block. #631
  • Applies to both position and size targets.
  • This attribute can take any length or percentage, which specifies the minimum distance between the target and the edges of its containing block. Each side can be specified individually, and negative values are allowed. See the documentation for details.
  • Defaults to 0px, which means that handle targets will now be constrained exactly to the edges of their containing block.
• Fix several issues where the element jolts some distance at drag start:
  • When the target's containing block has a border.
  • When the target is set to relative positioning and offset from the top-left corner.

New decorator: text

Implement a new decorator to render text as a background on elements. This can be particularly helpful when using icon fonts, and even allows using such fonts for generated elements. #348 #655 #679

decorator: text("Hello 🌎 world!" blue bottom right);

The font face will be inherited from the element it is being applied to. However, it can be colored independently. Further, the text can be freely aligned within the element using lengths, percentages, or keywords. Unicode numerical references are supported with the HTML syntax, e.g. 🌎.

Flexbox layout improvements

• Apply automatic minimum size of flex items in column mode with auto size. #658
• Performance improvement: Skip calculating hypothetical cross size when not needed. Avoids a potentially expensive formatting step in some situations. #658
• Fix the hypothetical width of replaced elements (such as images) in column direction layout. #666
• Fix hitting an assertion due to negative flex item size in some situations when the edge size is fractional. #657

Data binding

• Allow custom getter/setter on scoped enum. #693 #699 (thanks @AmaiKinono)
• Ternary expressions are now implemented with jumps so that only one branch is evaluated. This makes it possible to e.g. avoid invalid array access in case of an empty array. #740 (thanks @rminderhoud and @exjam)
• Fix an issue where the FamilyId would have the same value for different types across shared library boundaries, which could lead to a crash or other unexpected behavior.

Animations

• Add interpolation of color stop lists, which enables animation of color and position of stops in gradient decorators. #667
• Improve warning message when trying to animate box shadows. #688

RCSS Values

• Support hsl and hsla colors. E.g. color: hsl(30, 80%, 50%). #674 (thanks @AmaiKinono)

Input elements

• Implement the ability to style the progress of a range input. #736 (thanks @viseztrance)
  • A new sliderprogress child element is added for this purpose.
    
• Improve navigation of <select> elements when using controller/keyboard navigation. #565 #566 (thanks @Paril)
  • Scroll to the selected options as one is moving up or down the list.
  • Scroll to the selected option when opening up the selection box.
  • Add the ability to programmatically show or hide the selection box.
• Fix some layout and behavior issues of the <select> element.
  • Fix issues related to specifying the height of the select arrow element.
  • Fix an issue where the selection box would scroll to the top-left corner when the document layout is updated.
• Fix an issue where wrapping a <select> element inside a <label> element would prevent mouse clicks from being able to select a new option. #494
• Fix an issue where the contents of the <input type="text"> and <textarea> elements could sometimes inadvertently scroll to a new place after a layout update.
• Handle multi-byte characters in <input type="password"> fields. #735

Elements

• Add support for the :scope pseudo selector when calling into the Element DOM query methods, i.e. Element::QuerySelector[All], Element::Matches, and Element::Closest. #578 (thanks @Paril)
• Add Element::Contains DOM method.
• Allow Element::ScrollIntoView to only scroll in the nearest scroll container, instead of all ancestor scroll containers, by using the new ScrollParentage::Closest scroll option.
• Fix an issue where scrollbars could appear or disappear one frame after they should have changed visibility.

Documents

• Expose ElementDocument::FindNextTabElement publicly.
• Disallow focusing into an unloaded document to prevent a potential situation with dangling pointers. #730

Font engine

• Add the ability to select a font face from a font collection, using its face index passed to Rml::LoadFontFace. #720 (thanks @leduyquang753)
• Fix rare placement of glyphs appearing below the baseline in some fonts, by using the bitmap bearing instead of the glyph metrics.
• The HarfBuzz font engine now uses kerning from HarfBuzz instead of FreeType. #639 (thanks @TriangulumDesire)

RML Parsing and layouting

• Fix RML parsing of extra hyphen in closing comment, i.e. ---> instead of -->. #681
• Fix a crash during layouting with word break enabled, when the first character of a token is multi-byte and does not fit on the line. #753 (thanks @and3md)

Rendering

• Fix incorrect clipping when using multiple contexts of different dimensions. #677 #680 (thanks @s1sw)
• Defer texture loading until the texture becomes visible.

Backends

• Update the SFML backend to support SFML 3, in addition to the existing SFML 2 support.
  • By default, SFML 3 is preferred before SFML 2 during CMake configuration. To override the automatic selection, set the CMake variable RMLUI_SFML_VERSION_MAJOR to the desired version (2 or 3).
• Update all SDL backends to support SDL 3, in addition to the existing SDL 2 support.
  • By default, SDL 3 is preferred before SDL 2 during CMake configuration. To override the automatic selection, set the CMake variable RMLUI_SDL_VERSION_MAJOR to the desired version (2 or 3).
• SDL 3-specific improvements:
  • Enable high DPI support.
  • Enable positioning of the input method editor (IME) to the text cursor.
• Improvements to both SDL 2 and SDL 3:
  • Keyboard is activated and deactivated when focusing text input fields.
  • Text input events are only submitted when text input fields are focused.
• SDL_GL2-specific improvements:
  • GLEW is no longer required, and no longer linked to.
  • Use OpenGL directly instead of the SDL renderer, just like the SDL_GL3 renderer.
• OpenGL 3 renderer-specific improvements:
  • Added the ability to set an offset with the call to SetViewport(). #724 (thanks @viseztrance)
  • Added RMLUI_NUM_MSAA_SAMPLES as a customizable macro for the number of MSAA samples to use in RmlUi framebuffers.
  • Added utility functions GetTransform() and ResetProgram() to more easily enable client projects to render with their own shaders.

Plugins

• Log warnings when SVG or Lottie files cannot be rendered. #687
• Support for LunaSVG 3.0 with the SVG plugin.

Unit testing

• Enable shell renderer with environment variable RMLUI_TESTS_USE_SHELL=1 instead of a compile definition.

Resource management

• Avoid memory allocations during global initialization. #689
  • Instead, explicitly start lifetime of globals during the call to Rml::Initialise.
  • Thus, there should no longer be any memory allocations occurring before main() when linking to RmlUi.
  • We now give a warning if there are objects in user space that refer to any RmlUi resources at the end of Rml::Shutdown, as this prevents the library from cleaning up memory pools.
    • We make an exemption for Rml::EventListener as those are commonly kept around until after Rml::Shutdown which is considered reasonable.
• Add manual release of render managers, Rml::ReleaseRenderManagers, to allow the render interface to be destroyed before Rml::Shutdown. #703

Building

• Remove OpenGL::GL dependency for GL3 backends. #684 (thanks @std-microblock)
• Fix dependency check signature in RmlUiConfig causing failure to find dependencies. #721 #722 (thanks @mpersano)
• Log to console by default when building on MinGW. #757 (thanks @trexxet)
• Fix a missing header include in the GL3 renderer, causing a compilation error on Visual Studio 17.12.
• Fix a build issue on certain Visual Studio 2017 setups by using std::enable_if_t consistently. #734
• Fix a build issue on Android with C++ 23 enabled due to mismatching std-namespace usage and C vs. C++ math headers.
• Fix unit tests and missing sample data when building with Emscripten.
• Libraries and archives will now be placed in the top-level binary directory, unless overridden by users or parent projects. This matches the existing runtime output directory.

Readme

• Improve readme code examples. #683 (thanks @std-microblock)

Breaking changes

• Layouts may see 1px shifts in various places due to the improvements to prevent single pixel gaps.
• The target of the <handle> element will no longer move outside its containing block by default, see above for how to override this behavior.
• Changed the signature of MeshUtilities::GenerateBackground and MeshUtilities::GenerateBackgroundBorder.
  • They now take the new RenderBox class as input. The Element::GetRenderBox method can be used to construct it.
• Changed ComputedValues::border_radius to return an array instead of Vector4f.
• Rml::ReleaseMemoryPools is no longer exposed publicly. This function is automatically called during shutdown and should not be used manually.
• SDL backends: The SDL platform's InputEventHandler function now takes an additional parameter window.

New Contributors

• @AmaiKinono made their first contribution in #674
• @s1sw made their first contribution in #680
• @std-microblock made their first contribution in #683
• @mpersano made their first contribution in #721
• @leduyquang753 made their first contribution in #720
• @rminderhoud made their first contribution in #740
• @and3md made their first contribution in #753
• @trexxet made their first contribution in #757

Full Changelog: 6.0...6.1