Add a "Fit" button to the status bar
The zoom actions for "Fit", "Fill" and "100%" were recently moved from status bar to a common popup also available on the status bar in 2c829f4e. There was some criticism of this change because users found it unnecessarily cumbersome that they now needed an extra click to invoke these common actions.
This commit re-adds a "Fit" button on the status bar. It is a toggle button and unchecking it will switch to "100%".
There is some criticism that this commit doesn't also re-add the "Fill" and "100%" buttons. I will explain my reasons for not adding them but this doesn't reflect a reached consensus and can therefore not be a final decision.
I am interested in merging this as it is anyway because nobody was against adding a "Fit" button.
The reasons why this commit re-adds a "Fit" button but neither a "Fill" nor "100%" button are as follows:
"Fit" is the default way to view an image in Gwenview. It allows users to get the full picture which in many cases is the most important way to view an image. Whenever any zoom changes were done this button will allow to quickly jump back to seeing the whole image.
Zooming to "100%" is considered to be a lot less useful in many situations. 1. The zoom value is identical to Fit for images smaller than the view area. 2. Because of the previous, having both a "100%" and "Fit" button can be confusing because changing between them does seemingly nothing even though having these buttons side by side implies that it would. 3. For pictures made with typical cameras/phones nowadays 100% zoom is very zoomed in and not automatically any more useful than e.g. 50% zoom. For these reasons no "100%" button is added by this commit. However the "Fit" action always worked in a way that unchecking it zooms to 100% so zooming to 100% is now also only one click away even though no explicit "100%" button is added.
Concerning the "Fill" action: I didn't see a lot of comments of people being bothered by its removal from the status bar. Using it might be an aquired taste and there might be some people that use it a lot but it doesn't seem like it is very popular currently. Users are encouraged to add a "Fill" button to their personal toolbar or to "scroll down" on the new ZoomComboBox.
FIXED-IN: 22.04