Mattermost-server: Migrate changeCSS() to CSS variable in utils/utils.jsx, ln. 566

[deanwhillier]

Context:

We are working on replacing our older custom theme implementation (applyTheme()) currently used to change component colors throughout the webapp to match the selected theme. We have decided to utilize CSS variables as a replacement and so we now need to replace all occurances of changeCSS() within the applyTheme() function with corresponding CSS variables directly in the CSS files. This ticket is part of a larger campaign.

How to migrate

Go to line number 566 in the file utils/utils.jsx. You should see the following:

changeCss('.team-sidebar .fa', 'color:' <ins> theme.sidebarHeaderTextColor);

For this ticket, we will be replacing the use of the Javascript variable theme.sidebarHeaderTextColor from this line of code with the CSS variable --sidebar-header-text-color. Please work off the branch campaign/applytheme_sidebar-header-text-color to avoid conflicts with other tickets for the same campaign.

Run through these steps to determine where to apply the new CSS variable followed by removing the call to changeCSS() from utils/utils.jsx:

1. Make note of the CSS statement from the first argument to changeCSS and specifically the final selector (eg. .app__body .sidebar--menu)
2. Using your browsers dev tools, locate the element targeted by the css statement in the webapp
3. With the element selected in your dev tools, use the style browser to get an idea of how styles are currently applied to this element. This will help you track down where in the source code you will need to add the appropriate CSS variable in order to replace the style identified in the second argument to changeCSS() above (eg. 'background:' </ins> theme.sidebarBg)
4. Locate the appropriate file(s) within the source code where edits will need to be made (eg. sass/layout/_sidebar-menu.scss, ln.3)
5. Make the necessary changes/additions to the CSS to apply the CSS variable and then remove the call to changeCSS() from utils/utils.jsx.
6. Create a pull request with your changes against the branch campaign/applytheme_sidebar-header-text-color. We will be using this branch to review and QA changes in batches on a regular basis instead of on each individual ticket in the campaign given the number of overall tickets for this campaign.

Notes:

• Some instances of changeCSS() affect the styles of sections of the UI that might not be visible by default. Remember to check modals, pop-ups, menus and different interaction states (hover, active, etc.) as necessary based on the particular ticket you are working on
• Some instances of changeCSS() include the use of a custom changeOpacity() function when applying colours that need to be partially transparent. These instances will need to be replaced with the rgba CSS function. For example, changeOpacity(theme.sidebarBg, 0.3)) in utils/utils.jsx would become rgba(var(--sidebar-bg-rgb), 0.3) in CSS. Appending -rgb to the CSS variable name is necessary when using one of the theme variables to work with the rgba CSS function.
• Some UI elements in the desktop web view will actually be different elements in the mobile web view, eg. the desktop and mobile primary/hamburger menus have completely separate markup
• Please be sure to test the primary responsive breakpoint widths after migration (Desktop: 1920px, Tablet: 960px, Mobile: 768px)
• Please be sure to test changing themes after migration to ensure the new CSS variable is being applied correctly. Switching back and forth between light and dark themes would be a good way to help determine this. Responsive breakpoints should also be tested with different themes.
• It is possible that an existing changeCSS() line is no longer valid, in which case, just removing the line as part of your PR is a perfectly valid solution.

Example of migrated code

PR #6655

• This PR includes several commits that each address a slightly different CSS statement in order to provide several examples of differing situations and how they were migrated. We suggest taking a look at each to get an idea of possible differences you could run across and how the resulting migration was accomplished.

Questions

Feel free to ask for help by messaging either @deanwhillier or @hmhealey or by posting in the ~webapp channel on the Mattermost Community server.

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JIRA ticket: https://mattermost.atlassian.net/browse/MM-29465

[prazolpp]

Hello @deanwhillier , I'd be happy to take this one on!

[deanwhillier]

It’s all yours @prazolpp, thanks!

[prazolpp]

It looks like the utils/utils.jsx file is in the mattermost/mattermost-webapp repo though

[hmhealey]

Yeah, that's correct. We currently put web app Help Wanted tickets here since the server and web app are pretty tightly coupled and because many of them require changes to both repositories. This one just requires web app changes though