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Add delta capper.

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This commit is contained in:
Thomas Harte 2023-08-20 15:32:48 -04:00
parent 1125286b96
commit 3e2a82b638
1 changed files with 20 additions and 11 deletions
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31
Machines/Apple/ADB/Mouse.cpp
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@ -15,24 +15,34 @@ using namespace Apple::ADB;
Mouse::Mouse(Bus &bus) : ReactiveDevice(bus, 3) {}
void Mouse::perform_command(const Command &command) {
if(command.type == Command::Type::Talk && command.reg == 0) {
// Read current deltas and buttons, thread safely.
auto delta_x = delta_x_.exchange(0);
auto delta_y = delta_y_.exchange(0);
const int buttons = button_flags_;
static constexpr int16_t max_delta = 30;
// Clamp deltas.
delta_x = std::clamp(delta_x, int16_t(-128), int16_t(127));
delta_y = std::clamp(delta_y, int16_t(-128), int16_t(127));
if(command.type == Command::Type::Talk && command.reg == 0) {
// Read and clamp current deltas and buttons.
//
// There's some small chance of creating negative feedback here — taking too much off delta_x_ or delta_y_
// due to a change in the underlying value between the load and the arithmetic. But if that occurs it means
// the user moved the mouse again in the interim, so it'll just play out as very slight latency.
auto delta_x = delta_x_.load(std::memory_order::memory_order_relaxed);
auto delta_y = delta_y_.load(std::memory_order::memory_order_relaxed);
if(abs(delta_x) > max_delta || abs(delta_y) > max_delta) {
int max = std::max(abs(delta_x), abs(delta_y));
delta_x = delta_x * max_delta / max;
delta_y = delta_y * max_delta / max;
}
const int buttons = button_flags_.load(std::memory_order::memory_order_relaxed);
delta_x_ -= delta_x;
delta_y_ -= delta_y;
// Figure out what that would look like, and don't respond if there's
// no change to report.
// no change or deltas to report.
const uint16_t reg0 =
((buttons & 1) ? 0x0000 : 0x8000) |
((buttons & 2) ? 0x0000 : 0x0080) |
uint16_t(delta_x & 0x7f) |
uint16_t((delta_y & 0x7f) << 8);
if(reg0 == last_posted_reg0_) return;
if(!(reg0 & 0x7f7f) && (reg0 & 0x8080) == (last_posted_reg0_ & 0x8080)) return;
// Post change.
last_posted_reg0_ = reg0;
@ -41,7 +51,6 @@ void Mouse::perform_command(const Command &command) {
}
void Mouse::move(int x, int y) {
// TODO: cap movement speed, feeding changes in slowly.
delta_x_ += int16_t(x);
delta_y_ += int16_t(y);
post_service_request();