Automation Editor point fine tuning with wheel scroll

[tecknixia]

Related to issue #5225
And replaces old PR #5232

Allows user to place cursor over an automation point in the Automation Editor, and use scroll wheel to adjust the y level for that point. It also improves mouse cursor interaction with the point, and shows the point's Y level when mouse cursor is over a point.

https://cdn.discordapp.com/attachments/332258319228207114/629248936099708928/AutomationEditor2-2019-10-03_04.21.20.mp4 (example, not current)

This PR involves the creation of a variable, and the use of mouseMoveEvent, drawCross, and wheelEvent.

• A variable, m_pointYLevel is created and used to hold a point's Y level position.
• The value of m_pointYLevel is set when the mouse moves over a point.
• The value of m_pointYLevel changes when the mouse wheel is scrolled, and over a point.
• The point's Y level changes when the mouse wheel is scrolled, and over a point.
• If the mouse moves away from a point, the value of m_pointYLevel returns to 0.
• When the value of m_pointYLevel is 0, the tool tip in drawCross displays the Y level position of the mouse.
• When the value of m_pointYLevel is greater than 0, the tool tip in drawCross displays the point's Y level position.

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Linux

• Linux (AppImage): lmms-1.2.1.569-linux-x86_64.AppImage (build link)

Windows

• Windows 32-bit: lmms-1.2.1.569-mingw-win32.exe (build link)
• Windows 64-bit: lmms-1.2.1.569-mingw-win64.exe (build link)
• Windows 32-bit: lmms-1.2.1-msvc2017-win32.exe (build link)
• Windows 64-bit: lmms-1.2.1-msvc2017-win64.exe (build link)

macOS

• macOS : lmms-1.2.1.569-mac10.13.dmg (build link)

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[tecknixia]

@russiankumar #5592
Issue with macos, not sure how to resolve.
Double clicking is good enough. ( #5292 )
This PR is not as important. In fact, I just realized that it would be better if the automation point was able to be selected before using the scroll wheel so it doesn't interfere with scrolling on the y-axis.
This PR can be closed.

[ryuukumar]

Ah, I believe we’ve dropped the overhaul for now. If you need to work on something you can do so, there’s no hurry for now.

[IanCaio]

@russiankumar #5592
Issue with macos, not sure how to resolve.
Double clicking is good enough. ( #5292 )
This PR is not as important. In fact, I just realized that it would be better if the automation point was able to be selected before using the scroll wheel so it doesn't interfere with scrolling on the y-axis.
This PR can be closed.

Closing this PR in favor of the other one as suggested by the author!