Kernel+WindowServer: Move mouse input signal parsing to kernel driver.

It was silly for the WindowServer to have to know anything about the
format of PS/2 mouse packets.

This patch also enables use of the middle mouse button.

Kernel/MousePacket.h

@@ -0,0 +1,7 @@
+#pragma once
+
+struct MousePacket {
+    int dx { 0 };
+    int dy { 0 };
+    byte buttons;
+};

Kernel/PS2MouseDevice.cpp

@@ -62,14 +62,35 @@ void PS2MouseDevice::handle_irq()
                 m_queue.size()
             );
 #endif
-            m_queue.enqueue(m_data[0]);
-            m_queue.enqueue(m_data[1]);
-            m_queue.enqueue(m_data[2]);
+            parse_data_packet();
             break;
         }
     }
 }
 
+void PS2MouseDevice::parse_data_packet()
+{
+    int x = m_data[1];
+    int y = m_data[2];
+    bool x_overflow = m_data[0] & 0x40;
+    bool y_overflow = m_data[0] & 0x80;
+    bool x_sign = m_data[0] & 0x10;
+    bool y_sign = m_data[0] & 0x20;
+    if (x && x_sign)
+        x -= 0x100;
+    if (y && y_sign)
+        y -= 0x100;
+    if (x_overflow || y_overflow) {
+        x = 0;
+        y = 0;
+    }
+    MousePacket packet;
+    packet.dx = x;
+    packet.dy = y;
+    packet.buttons = m_data[0] & 0x07;
+    m_queue.enqueue(packet);
+}
+
 void PS2MouseDevice::wait_then_write(byte port, byte data)
 {
     prepare_for_output();
@@ -150,8 +171,12 @@ ssize_t PS2MouseDevice::read(Process&, byte* buffer, ssize_t size)
     while (nread < size) {
         if (m_queue.is_empty())
             break;
-        // FIXME: Don't return partial data frames.
-        buffer[nread++] = m_queue.dequeue();
+        // Don't return partial data frames.
+        if ((size - nread) < (ssize_t)sizeof(MousePacket))
+            break;
+        auto packet = m_queue.dequeue();
+        memcpy(buffer, &packet, sizeof(MousePacket));
+        nread += sizeof(MousePacket);
     }
     return nread;
 }

Kernel/PS2MouseDevice.h

@@ -1,7 +1,8 @@
 #pragma once
 
 #include <Kernel/CharacterDevice.h>
-#include "IRQHandler.h"
+#include <Kernel/MousePacket.h>
+#include <Kernel/IRQHandler.h>
 
 class PS2MouseDevice final : public IRQHandler, public CharacterDevice {
 public:
@@ -30,8 +31,9 @@ private:
     byte mouse_read();
     void wait_then_write(byte port, byte data);
     byte wait_then_read(byte port);
+    void parse_data_packet();
 
-    CircularQueue<byte, 600> m_queue;
+    CircularQueue<MousePacket, 100> m_queue;
     byte m_data_state { 0 };
-    signed_byte m_data[3];
+    byte m_data[3];
 };

WindowServer/WSMessageLoop.cpp

@@ -6,6 +6,7 @@
 #include <WindowServer/WSClientConnection.h>
 #include <WindowServer/WSAPITypes.h>
 #include <Kernel/KeyCode.h>
+#include <Kernel/MousePacket.h>
 #include <LibC/sys/socket.h>
 #include <LibC/sys/select.h>
 #include <LibC/unistd.h>
@@ -200,45 +201,35 @@ void WSMessageLoop::drain_mouse()
     auto& screen = WSScreen::the();
     bool prev_left_button = screen.left_mouse_button_pressed();
     bool prev_right_button = screen.right_mouse_button_pressed();
+    bool prev_middle_button = screen.middle_mouse_button_pressed();
     int dx = 0;
     int dy = 0;
     bool left_button = prev_left_button;
     bool right_button = prev_right_button;
+    bool middle_button = prev_middle_button;
     for (;;) {
-        byte data[3];
-        ssize_t nread = read(m_mouse_fd, data, sizeof(data));
+        MousePacket packet;
+        ssize_t nread = read(m_mouse_fd, &packet, sizeof(MousePacket));
         if (nread == 0)
             break;
-        ASSERT(nread == sizeof(data));
-        bool left_button = data[0] & 1;
-        bool right_button = data[0] & 2;
-        bool x_overflow = data[0] & 0x40;
-        bool y_overflow = data[0] & 0x80;
-        bool x_sign = data[0] & 0x10;
-        bool y_sign = data[0] & 0x20;
+        ASSERT(nread == sizeof(packet));
+        left_button = packet.buttons & 1;
+        right_button = packet.buttons & 2;
+        middle_button = packet.buttons & 4;
 
-        if (x_overflow || y_overflow)
-            continue;
-
-        int x = data[1];
-        int y = data[2];
-        if (x && x_sign)
-            x -= 0x100;
-        if (y && y_sign)
-            y -= 0x100;
-
-        dx += x;
-        dy += -y;
-        if (left_button != prev_left_button || right_button != prev_right_button) {
+        dx += packet.dx;
+        dy += -packet.dy;
+        if (left_button != prev_left_button || right_button != prev_right_button || middle_button != prev_middle_button) {
             prev_left_button = left_button;
             prev_right_button = right_button;
-            screen.on_receive_mouse_data(dx, dy, left_button, right_button);
+            prev_middle_button = middle_button;
+            screen.on_receive_mouse_data(dx, dy, left_button, right_button, middle_button);
             dx = 0;
             dy = 0;
         }
     }
     if (dx || dy) {
-        screen.on_receive_mouse_data(dx, dy, left_button, right_button);
+        screen.on_receive_mouse_data(dx, dy, left_button, right_button, middle_button);
     }
 }
 

WindowServer/WSScreen.cpp

@@ -58,28 +58,24 @@ void WSScreen::set_resolution(int width, int height)
     m_cursor_location.constrain(rect());
 }
 
-void WSScreen::on_receive_mouse_data(int dx, int dy, bool left_button, bool right_button)
+void WSScreen::on_receive_mouse_data(int dx, int dy, bool left_button, bool right_button, bool middle_button)
 {
     auto prev_location = m_cursor_location;
     m_cursor_location.move_by(dx, dy);
     m_cursor_location.constrain(rect());
-    if (m_cursor_location.x() >= width())
-        m_cursor_location.set_x(width() - 1);
-    if (m_cursor_location.y() >= height())
-        m_cursor_location.set_y(height() - 1);
     unsigned buttons = 0;
     if (left_button)
         buttons |= (unsigned)MouseButton::Left;
     if (right_button)
         buttons |= (unsigned)MouseButton::Right;
-    if (m_cursor_location != prev_location) {
-        auto message = make<WSMouseEvent>(WSMessage::MouseMove, m_cursor_location, buttons);
-        WSMessageLoop::the().post_message(WSWindowManager::the(), move(message));
-    }
+    if (middle_button)
+        buttons |= (unsigned)MouseButton::Middle;
     bool prev_left_button = m_left_mouse_button_pressed;
     bool prev_right_button = m_right_mouse_button_pressed;
+    bool prev_middle_button = m_middle_mouse_button_pressed;
     m_left_mouse_button_pressed = left_button;
     m_right_mouse_button_pressed = right_button;
+    m_middle_mouse_button_pressed = middle_button;
     if (prev_left_button != left_button) {
         auto message = make<WSMouseEvent>(left_button ? WSMessage::MouseDown : WSMessage::MouseUp, m_cursor_location, buttons, MouseButton::Left);
         WSMessageLoop::the().post_message(WSWindowManager::the(), move(message));
@@ -88,6 +84,15 @@ void WSScreen::on_receive_mouse_data(int dx, int dy, bool left_button, bool righ
         auto message = make<WSMouseEvent>(right_button ? WSMessage::MouseDown : WSMessage::MouseUp, m_cursor_location, buttons, MouseButton::Right);
         WSMessageLoop::the().post_message(WSWindowManager::the(), move(message));
     }
+    if (prev_middle_button != middle_button) {
+        auto message = make<WSMouseEvent>(middle_button ? WSMessage::MouseDown : WSMessage::MouseUp, m_cursor_location, buttons, MouseButton::Middle);
+        WSMessageLoop::the().post_message(WSWindowManager::the(), move(message));
+    }
+    if (m_cursor_location != prev_location) {
+        auto message = make<WSMouseEvent>(WSMessage::MouseMove, m_cursor_location, buttons);
+        WSMessageLoop::the().post_message(WSWindowManager::the(), move(message));
+    }
+    // NOTE: Invalidate the cursor if it moved, or if the left button changed state (for the cursor color inversion.)
     if (m_cursor_location != prev_location || prev_left_button != left_button)
         WSWindowManager::the().invalidate_cursor();
 }

WindowServer/WSScreen.h

@@ -26,8 +26,9 @@ public:
     Point cursor_location() const { return m_cursor_location; }
     bool left_mouse_button_pressed() const { return m_left_mouse_button_pressed; }
     bool right_mouse_button_pressed() const { return m_right_mouse_button_pressed; }
+    bool middle_mouse_button_pressed() const { return m_middle_mouse_button_pressed; }
 
-    void on_receive_mouse_data(int dx, int dy, bool left_button, bool right_button);
+    void on_receive_mouse_data(int dx, int dy, bool left_button, bool right_button, bool middle_button);
     void on_receive_keyboard_data(KeyEvent);
 
 private:
@@ -40,6 +41,7 @@ private:
     Point m_cursor_location;
     bool m_left_mouse_button_pressed { false };
     bool m_right_mouse_button_pressed { false };
+    bool m_middle_mouse_button_pressed { false };
 };
 
 inline RGBA32* WSScreen::scanline(int y)