drawTransparentChar glitch

[ImpulseAdventure]

Describe the bug
Hi Martin -- thanks for putting together this optimized library for the ILI9225!

I am in the process of adding support for ILI9225_Due to the GUIslice GUI library but have encountered user reports that suggest an issue exists involving font rendering in the transparent mode. Although I have not yet set up my own ILI9225 to test this scenario, I am filing this issue speculatively under the expectation that the issue likely exists in the same manner as I observed in the upstream source. (You can run the attached example sketch below to confirm whether or not it applies).

Fonts that have the high-order bit set in the vertical raster, followed by a blank (padded) column, will cause a vertical line glitch in the padded column. This is due to a bug in drawTransparentChar() that I had identified and fixed in Marek's upstream ILI9341_Due library; though the corresponding fix doesn't appear to exist in the derived ILI9225_Due version.

If you confirm that the issue exists (from my example sketch), I will submit a PR for you that should hopefully fix the glitch -- applying a similar patch as I did for Marek's library

To Reproduce

• Please try running the sample sketch I created and let me know if you observe the problem.
• ILI9225_due-font-glitch.zip
• Note that I have not yet run this on an ILI9225, but based on my experience with ILI9341_Due, I believe this code might trigger the failure case.

Expected behavior
No vertical glitches appearing after transparent characters are rendered.

Screenshots
Example of the glitch (as generated during my ILI9341_Due investigation):

Library:

• ILI9225_Due latest master e265904
• Note that I have not yet tried recreating this issue on the ILI9225 hardware yet

Thanks for your time!
Cal

[ImpulseAdventure]

FYI -- a user has confirmed to me that the attached ILI9225_due-font-glitch.zip proof-of-concept sketch does generate the glitch on their ILI9225 display.

Let me know if you might be interested in testing out a possible fix at some point (no rush).
thanks