As anticipated, I produced a new modification of the original Onyx "Monitor" application.
This one reacts upon touch in the four corners of the screen, as follows:
-- NW corner, NE corner: refresh the screen;
-- SW corner: set "Normal" mode (Regal);
-- SE corner: set "A2" mode ("Fast Mode");
-- middle (elsewhere): open menu, just like in the original.
Code:
+--------------------------------+
| Refr. | | Refr. |
| | | |
|-------| |-------|
| |
| Menu |
| |
|-------| |-------|
| Norm. | | A2 |
| | | |
+--------------------------------+
I have to say, with these modifications I find the "(HDMI) Monitor" capabilities quite satisfactory, unless one asks the impossible... The A2 mode is fast enough, (although to use the mouse cursor with precision remains not the easiest), and the Normal mode has the satisfactory rendering quality (although it is advised to keep a high resolution to avoid softened edges). You can switch to A2 or Normal any time by tapping on the relevant corner.
What is left to do is an implementation of the touchscreen as a pointing device, so instead of being forced to a mouse (pad etc.) one could use the pen or finger to interact with the desktop icons, application controls etc. As Onyx recommends to connect the USB cable anyway...
I am still experiencing a "pulsating" effect in A2 and a "flashing stripes" effect in Normal mode, but it is comforting to know that "it's just my system" (further confirmations appreciated).
I attach here the modified APK (zipped to upload it).
Disclaimer: I take no responsibility etc.
I also attach the file I injected to make the modification, for the interested.