PlantUML: Fixing 'back:' Attribute In Titles

Hey everyone! Have you ever run into a snag while trying to customize your PlantUML diagrams? Today, we're diving deep into a specific issue: the back: HTML attribute not working as expected within the title section. Let's break down the problem, explore potential solutions, and discuss how to make your PlantUML titles shine!

Understanding the Issue with back: in PlantUML Titles

So, you're trying to spice up your PlantUML diagrams, and you've decided to start with the title. You've read the documentation, and it seems like the <back:Red>Text</back> attribute should allow you to change the background color of specific text portions within your title. But, alas, it's not working! This can be super frustrating, especially when you're aiming for a specific look and feel.

The core of the problem lies in how PlantUML processes and renders HTML-like attributes within the title context. While attributes like <color:Red> might work fine, back: seems to be a bit more stubborn. The user in our example tried using it in combination with other attributes like <size:24>, but even on its own, <back:Red> refuses to play ball. This inconsistency can leave you scratching your head, wondering what's going on.

To illustrate the issue, let's revisit the original PlantUML code snippet:

@startuml
<style>
title {
 FontName Arial
 HorizontalAlignment center
 FontSize 12
}
.subtitle1 {
 Backgroundcolor Red
 FontColor Black
}
.subtitle2 {
 Backgroundcolor Black
 FontColor White
}
</style>
title
To create a subtitle with different Style
<back:Red><size:24>back:Red</size></back>
<color:Red>color:Red</color>
end title
@enduml

The output clearly demonstrates that the back: attribute is ignored, while the <color:Red> attribute works as expected. This discrepancy highlights the need for a solution, whether it's fixing the back: attribute itself or providing alternative ways to style titles and subtitles.

Exploring Potential Solutions and Workarounds

Now that we've identified the problem, let's brainstorm some potential solutions. The original poster suggested a few excellent options, which we'll explore in detail:

1. Fixing the back: Attribute

The most straightforward solution, of course, would be to fix the back: attribute so it works as documented within the title section. This would involve diving into PlantUML's codebase and figuring out why this specific attribute isn't being processed correctly. It could be a parsing issue, a rendering bug, or simply an oversight in the implementation. A fix here would ensure consistency and allow users to style their titles as intended.

2. Introducing a subtitle Style

Another elegant solution would be to introduce a dedicated subtitle style, similar to how the title style works. This would allow users to define specific formatting rules for subtitles, including background color, font size, and more. The syntax could mirror the title syntax, perhaps using subtitle ... end subtitle blocks to encapsulate the subtitle text and its styling.

For example:

@startuml
<style>
subtitle {
 Backgroundcolor Green
 FontColor White
 FontSize 18
}
</style>

title My Main Title
subtitle
This is a Subtitle with a Green Background
end subtitle

@enduml

This approach would provide a clean and intuitive way to create visually distinct subtitles within PlantUML diagrams.

3. Applying Styles to Text Lines

A more flexible approach would be to allow users to apply predefined styles to individual text lines within a diagram. This could be achieved using a syntax like <<subtitle1>> This is a styled line, where subtitle1 refers to a predefined style (as shown in the original code snippet).

However, as the original poster noted, there isn't currently a way to apply styles to text lines in this manner. Implementing this feature would require extending PlantUML's syntax and processing capabilities, but it would offer a powerful way to customize the appearance of various text elements within a diagram.

4. Workarounds and Alternative Approaches

While we wait for a formal solution, there might be some workarounds we can explore. One approach could involve using HTML tables or other creative formatting techniques to simulate the desired background color effect. However, these workarounds might be cumbersome and less elegant than a direct solution.

Another approach could be to use an external image editor to create the title with the desired styling and then include it in the diagram. This is definitely less ideal as it adds an external dependency and makes the diagram less self-contained.

The Importance of Consistent Styling

The underlying theme here is the importance of consistent styling across PlantUML diagrams. When styling options are inconsistent or unpredictable, it can lead to frustration and make it harder to create visually appealing and informative diagrams. Supporting styles in a uniform way across all elements, including titles, subtitles, and text lines, would greatly enhance the user experience.

Imagine being able to apply a consistent style to all your headings, subheadings, and even specific keywords within your diagrams. This level of control would not only make your diagrams look more professional but also improve their readability and impact.

Diving Deeper: Why back: Might Behave Differently

Let's take a moment to speculate on why the back: attribute might be behaving differently from other HTML-like attributes. It's possible that the rendering engine PlantUML uses has specific rules for handling background colors, especially within the context of titles. Background colors can interact with other styling elements, such as borders and padding, in complex ways, so it's possible that the back: attribute requires special handling that hasn't been fully implemented in the title rendering logic.

Another possibility is that the back: attribute is being parsed correctly but is not being translated into the appropriate rendering commands. PlantUML might use a different mechanism for setting background colors compared to other attributes like font color or size. Understanding the internal workings of PlantUML's rendering engine is crucial for pinpointing the exact cause of this issue.

The Path Forward: A Community Effort

Ultimately, resolving this issue will likely require a community effort. PlantUML is an open-source project, and contributions from users like you are essential for its continued improvement. If you're a developer, consider diving into the codebase and exploring potential solutions. Even if you're not a coder, you can contribute by reporting bugs, suggesting improvements, and participating in discussions like this one.

The original poster's suggestions are a great starting point for a potential fix. By working together, we can make PlantUML even more powerful and user-friendly.

Summing Up: Taming the Title Styling Beast

In conclusion, the issue with the back: attribute in PlantUML titles highlights the importance of consistent styling and the need for clear and predictable behavior. While the current situation can be frustrating, there are several potential solutions, including fixing the back: attribute, introducing a subtitle style, and allowing styles to be applied to text lines.

Until a formal solution is implemented, we might need to rely on workarounds. However, by discussing the issue, exploring potential fixes, and contributing to the PlantUML community, we can pave the way for a more robust and versatile diagramming experience.

So, guys, let's keep the conversation going! Have you encountered this issue? Do you have any other ideas for styling PlantUML titles? Share your thoughts in the comments below, and let's work together to make PlantUML even better!