From 032018ec48dd6b1ef3cdc501342379061819d80b Mon Sep 17 00:00:00 2001
From: Francesco Abbate <francesco.bbt@gmail.com>
Date: Sat, 17 Apr 2021 14:57:04 -0700
Subject: [PATCH] More aggressive wait_event timeout when window has focus

Adopt a time based logic for cursor blinking and wait for event

when idle with a timeout equal to blink remaining time.
---
 data/core/docview.lua | 16 ++++++++--------
 data/core/init.lua    | 15 ++++++++++++---
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/data/core/docview.lua b/data/core/docview.lua
index 2c33d0a3..5552b652 100644
--- a/data/core/docview.lua
+++ b/data/core/docview.lua
@@ -55,7 +55,6 @@ function DocView:new(doc)
   self.doc = assert(doc)
   self.font = "code_font"
   self.last_x_offset = {}
-  self.blink_timer = 0
 end
 
 
@@ -244,7 +243,7 @@ function DocView:on_mouse_pressed(button, x, y, clicks)
     self.doc:set_selection(mouse_selection(self.doc, clicks, line, col, line, col))
     self.mouse_selecting = { line, col, clicks = clicks }
   end
-  self.blink_timer = 0
+  core.blink_reset()
 end
 
 
@@ -284,18 +283,18 @@ function DocView:update()
     if core.active_view == self then
       self:scroll_to_make_visible(line, col)
     end
-    self.blink_timer = 0
+    core.blink_reset()
     self.last_line, self.last_col = line, col
   end
 
   -- update blink timer
   if self == core.active_view and not self.mouse_selecting then
-    local n = config.blink_period / 2
-    local prev = self.blink_timer
-    self.blink_timer = (self.blink_timer + 1 / config.fps) % config.blink_period
-    if (self.blink_timer > n) ~= (prev > n) then
+    local T, t0 = config.blink_period, core.blink_start
+    local ta, tb = core.blink_timer, system.get_time()
+    if ((tb - t0) % T < T / 2) ~= ((ta - t0) % T < T / 2) then
       core.redraw = true
     end
+    core.blink_timer = tb
   end
 
   DocView.super.update(self)
@@ -348,8 +347,9 @@ function DocView:draw_line_body(idx, x, y)
   self:draw_line_text(idx, x, y)
 
   -- draw caret if it overlaps this line
+  local T = config.blink_period
   if line == idx and core.active_view == self
-  and self.blink_timer < config.blink_period / 2
+  and (core.blink_timer - core.blink_start) % T < T / 2
   and system.window_has_focus() then
     local lh = self:get_line_height()
     local x1 = x + self:get_col_x_offset(line, col)
diff --git a/data/core/init.lua b/data/core/init.lua
index d1118a45..442287df 100644
--- a/data/core/init.lua
+++ b/data/core/init.lua
@@ -403,6 +403,8 @@ function core.init()
   core.log_items = {}
   core.docs = {}
   core.threads = setmetatable({}, { __mode = "k" })
+  core.blink_start = system.get_time()
+  core.blink_timer = core.blink_start
 
   local project_dir_abs = system.absolute_path(project_dir)
   local set_project_ok = project_dir_abs and core.set_project_dir(project_dir_abs)
@@ -865,7 +867,6 @@ end)
 
 function core.run()
   local idle_iterations = 0
-  local frame_duration = 1 / config.fps
   while true do
     core.frame_start = system.get_time()
     local did_redraw = core.step()
@@ -878,7 +879,10 @@ function core.run()
       if idle_iterations > 1 then
         if system.window_has_focus() then
           -- keep running even with no events to make the cursor blinks
-          system.wait_event(frame_duration)
+          local t = system.get_time() - core.blink_start
+          local h = config.blink_period / 2
+          local dt = math.ceil(t / h) * h - t
+          system.wait_event(dt + 1 / config.fps)
         else
           system.wait_event()
         end
@@ -886,12 +890,17 @@ function core.run()
     else
       idle_iterations = 0
       local elapsed = system.get_time() - core.frame_start
-      system.sleep(math.max(0, frame_duration - elapsed))
+      system.sleep(math.max(0, 1 / config.fps - elapsed))
     end
   end
 end
 
 
+function core.blink_reset()
+  core.blink_start = system.get_time()
+end
+
+
 function core.on_error(err)
   -- write error to file
   local fp = io.open(USERDIR .. "/error.txt", "wb")