Changes
Added pseudo-code to help authors implement mouse support on CPC software
bit 1: Right Button (active low)
bit 2..7: unknown
== Review (German) ==
* "Bewundern Sie auch die Maussteuerung eines Atari ST oder eines Schneider PC? Bei Kempston gibt es für 69,95 Pfund auch für Ihren CPC oder Joyce so eine komfortable Benutzeroberfläche. Die Maus entspricht dabei völlig dem Standard mit zwei unabhängigen Tasten. Das mitgelieferte Desktop-Programm braucht sich vor den Brüdern auf 16-Bit-Computern nicht zu verstecken."
== Get mouse position on screen ==
Calculating the mouse position from the information given on the Kempston mouse ports is easy.
We will proceed in 2 steps:
1. Calculate mouse pointer location on a virtual screen that has a 640*400 resolution.
2. Translate position from the virtual screen to the current CPC screen mode.
Here is the algorithm in pseudo-code:
// initMouse initializes variables and centers the mouse pointer on screen
initMouse() {
maxX = 639;
maxY = 399;
// centering the mouse pointer on the screen
virtualX = maxX >> 1; // virtualX = maxX/2
virtualY = maxY >> 1; // virtualY = maxY/2
// store raw mouse values
oldX = inp(&FBEE);
oldY = inp(&FBEF);
// get mouse pointer position
refreshMouse();
}
// refreshMouse has to be called before you redraw the mouse pointer (ideally every frame)
refreshMouse() {
// get raw mouse values
rawX = inp(&FBEE);
rawY = inp(&FBEF);
// get the relative mouse displacement since last call
deltaX = rawX - oldX;
deltaY = rawY - oldY;
// store raw mouse values
oldX = rawX;
oldY = rawY;
// calculate new unclipped virtual position
virtualX = virtualX + deltaX;
virtualY = virtualY + deltaY;
// perform clipping
if (virtualX < 0) then virtualX = 0;
else if (virtualX > maxX) then virtualX = maxX;
if (virtualY < 0) then virtualY = 0;
else if (virtualY > maxY) then virtualY = maxY;
// now we translate position from the virtual screen to the current CPC screen mode
mouseY = virtualY >> 1; // mouseY = virtualY/2
if (mode2) then mouseX = virtualX;
else if (mode1) then mouseX = virtualX >> 1; // mouseX = virtualX/2
else if (mode0) then mouseX = virtualX >> 2; // mouseX = virtualX/4
}
[[Category:Peripherals]]
