TYPO3 Core

Whoops, the unfinished sentence should read:
Navigating within the Install Tool directly after changing the value does not trigger the effect, you have to re-enter the Install Tool completly (which immediatly triggers it).

It's not a bug, it's a feature :-)

typo3\sysext\install\Classes\Service\SilentConfigurationUpgradeService.php checks if GraphicsMagick is active, and return -1 for processor_effects for GM:

        if ((string)$currentProcessorValue !== '') {
            if ($currentProcessorMaskValue != 0) {
                $changedValues['GFX/processor_allowTemporaryMasksAsPng'] = 0;
            }
            if ($currentProcessorValue === 'GraphicsMagick') {
                if ($currentProcessorEffectsValue != -1) {
                    $changedValues['GFX/processor_effects'] = -1;
                }
            }
        }

This could be a historic decision because sharpen might not always be available to GM. The code is also active in the current master.

My two cents: We can remove this check, see current gm doc: http://www.graphicsmagick.org/GraphicsMagick.html#details-sharpen If a gm version does not support sharpen, you can disable this manually at processor_effects.

Patch set 1 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57324

Patch set 2 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57319

Patch set 3 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57319

Patch set 1 for branch TYPO3_8-7 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57339

Patch set 2 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57391

Patch set 3 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57391

Patch set 4 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57391

Patch set 1 for branch TYPO3_8-7 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57395