Fix SGR mouse reporting

There were two bugs fixed in this commit:

1. `sgr_mouse_report` was not always called when `SGR_MOUSE` bit was set
   due to calling `normal_mouse_report` instead of `mouse_report` in the
   scrolling method.
2. SGR reporting was always going off the left mouse button state rather
   than what was appropriate. This affected SGR scroll reporting since
   it only behaves correctly for pressed events (final character 'M').

Resolves alacritty#698.

src/input.rs

@@ -284,8 +284,9 @@ impl<'a, A: ActionContext + 'a> Processor<'a, A> {
                         && (
                             prev_line != self.ctx.mouse_mut().line
                             || prev_col != self.ctx.mouse_mut().column
-                        ) {
-                        self.mouse_report(32);
+                        )
+                {
+                    self.mouse_report(32, ElementState::Pressed);
                 }
             }
         }
@@ -308,18 +309,20 @@ impl<'a, A: ActionContext + 'a> Processor<'a, A> {
         }
     }
 
-    pub fn sgr_mouse_report(&mut self, button: u8, release: bool) {
+    pub fn sgr_mouse_report(&mut self, button: u8, state: ElementState) {
         let (line, column) = (self.ctx.mouse_mut().line, self.ctx.mouse_mut().column);
-        let c = if release { 'm' } else { 'M' };
+        let c = match state {
+            ElementState::Pressed => 'M',
+            ElementState::Released => 'm',
+        };
 
         let msg = format!("\x1b[<{};{};{}{}", button, column + 1, line + 1, c);
         self.ctx.write_to_pty(msg.into_bytes());
     }
 
-    pub fn mouse_report(&mut self, button: u8) {
+    pub fn mouse_report(&mut self, button: u8, state: ElementState) {
         if self.ctx.terminal_mode().contains(mode::TermMode::SGR_MOUSE) {
-            let release = self.ctx.mouse_mut().left_button_state != ElementState::Pressed;
-            self.sgr_mouse_report(button, release);
+            self.sgr_mouse_report(button, state);
         } else {
             self.normal_mouse_report(button);
         }
@@ -355,7 +358,7 @@ impl<'a, A: ActionContext + 'a> Processor<'a, A> {
                 self.ctx.clear_selection();
                 let report_modes = mode::TermMode::MOUSE_REPORT_CLICK | mode::TermMode::MOUSE_MOTION;
                 if !modifiers.shift && self.ctx.terminal_mode().intersects(report_modes) {
-                    self.mouse_report(0);
+                    self.mouse_report(0, ElementState::Pressed);
                     return;
                 }
 
@@ -368,7 +371,7 @@ impl<'a, A: ActionContext + 'a> Processor<'a, A> {
         let report_modes = mode::TermMode::MOUSE_REPORT_CLICK | mode::TermMode::MOUSE_MOTION;
         if !modifiers.shift && self.ctx.terminal_mode().intersects(report_modes)
         {
-            self.mouse_report(3);
+            self.mouse_report(3, ElementState::Released);
             return;
         }
 
@@ -429,7 +432,7 @@ impl<'a, A: ActionContext + 'a> Processor<'a, A> {
 
         let faux_scrollback_lines = self.mouse_config.faux_scrollback_lines;
         if self.ctx.terminal_mode().intersects(mouse_modes) {
-            self.normal_mouse_report(code);
+            self.mouse_report(code, ElementState::Pressed);
         } else if faux_scrollback_lines > 0 {
             // Faux scrolling
             let cmd = code + 1; // 64 + 1 = A, 65 + 1 = B