Microsoft Power Apps Canvas Apps, Power Fx Formulas, and Controls
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When a new screen looks like one you already have, duplicate it instead of building it again. Duplicate screen copies the screen with all its controls and formulas, and adds _1 to every name. Then you rename the copy and change what's different, starting with anything other screens send to the original.
On the narrowest phones, 360 pixels wide, my Power Apps app had three layout problems: a title cut in half, a button running off the screen, and list rows where a button left almost no room for the text. Each fix uses the screen's size, so phones get a tighter layout and larger screens stay as they were.
Incompatible types for comparison. These types can't be compared: Number, Error. means one side of a comparison has already failed. In my case, a duplicated screen compared a number with a context variable that only the original screen receives. The fix is to give the new screen its own variable.
This part builds the screen where a manager decides: approve a response, or decline it with a comment the employee sees. Then it tests the whole loop with a real employee in her own browser. That test found a bug: the employee didn't see her manager's decision. The fix, a Refresh button on every screen, ends the part.
On a phone, a header with two text buttons leaves little room for the title. The modern Button has a Layout property, and ButtonLayout.IconOnly shows just the icon. Switch to it only when the screen is phone-sized, ScreenSize.Small, and keep the button's accessible label.
A Refresh button lets people reload a screen's data without leaving it. The neat way to build one: move the screen's loading formula into the button's OnSelect, start it with Refresh, and make the screen's OnVisible select the button. Opening the screen and selecting Refresh then run the same formula.
Refresh gets a fresh copy of a data source, so the app shows changes other people made while it was running. It has no result, and it only works in formulas that run on an action, such as OnSelect and OnVisible. If your screen keeps data in variables, run its queries again after Refresh.
SharePoint gives every list item a number when it's created: its ID. To open one item on another screen, pass its ID with Navigate, and read the item there with LookUp(List, ID = ...). SharePoint can run that query itself, as long as you compare the ID with =.
A manager approved an employee's response, but the employee's screen kept saying Waiting for review, even after she opened it again. Microsoft documents why: a running canvas app doesn't pick up changes other people make. The fix is to call Refresh when a screen opens, and to give people a Refresh button for when they stay on a screen.
In Power Apps Studio, copying a control puts its code on the clipboard, and pasting creates a control from that code. If you copy anything else in between, such as a formula, the paste fails with There's something wrong with the pasted code. Check the code and try again. The fix is to copy the control again right before you paste it.
