chore: optimize framing algorithm

vhs.go

@@ -1,8 +1,8 @@
 package main
 
 import (
- "context"
  "fmt"
+ "log"
  "os"
  "os/exec"
  "path/filepath"
@@ -126,6 +126,8 @@ const cleanupWaitTime = 100 * time.Millisecond
 //
 // It also begins the rendering process of the frames into videos.
 func (vhs *VHS) Cleanup() {
+ vhs.PauseRecording()
+
  // Give some time for any commands executed (such as `rm`) to finish.
  //
  // If a user runs a long running command, they must sleep for the required time
@@ -158,64 +160,53 @@ func (vhs *VHS) Cleanup() {
  }
 }
 
-const quality = 0.92
-
 // Record begins the goroutine which captures images from the xterm.js canvases.
-func (vhs *VHS) Record(ctx context.Context) <-chan error {
- ch := make(chan error)
+func (vhs *VHS) Record() {
  interval := time.Second / time.Duration(vhs.Options.Video.Framerate)
- time.Sleep(interval)
+ save := vhs.frameSaver()
+ current := time.Now()
 
  go func() {
- counter := 0
- for {
- select {
- case <-ctx.Done():
- close(ch)
- return
-
- default:
- if !vhs.recording {
- time.Sleep(interval + interval)
- continue
- }
-
- if vhs.Page != nil {
- counter++
- start := time.Now()
- cursor, cursorErr := vhs.CursorCanvas.CanvasToImage("image/png", quality)
- text, textErr := vhs.TextCanvas.CanvasToImage("image/png", quality)
- if textErr == nil && cursorErr == nil {
- if err := os.WriteFile(
- filepath.Join(vhs.Options.Video.Input, fmt.Sprintf(cursorFrameFormat, counter)),
- cursor,
- os.ModePerm,
- ); err != nil {
- ch <- fmt.Errorf("error writing cursor frame: %w", err)
- }
- if err := os.WriteFile(
- filepath.Join(vhs.Options.Video.Input, fmt.Sprintf(textFrameFormat, counter)),
- text,
- os.ModePerm,
- ); err != nil {
- ch <- fmt.Errorf("error writing text frame: %w", err)
- }
- } else {
- ch <- fmt.Errorf("error: %v, %v", textErr, cursorErr)
- }
-
- elapsed := time.Since(start)
- if elapsed >= interval {
- continue
- } else {
- time.Sleep(interval - elapsed)
- }
- }
+ for vhs.recording {
+ if time.Since(current) >= interval {
+ current = time.Now()
+ go save()
  }
+ time.Sleep(time.Millisecond)
  }
  }()
+}
 
- return ch
+func (vhs *VHS) frameSaver() func() {
+ const quality = 0.92
+ counter := 0
+ lock := &sync.Mutex{}
+
+ return func() {
+ lock.Lock()
+ defer lock.Unlock()
+
+ cursor, cursorErr := vhs.CursorCanvas.CanvasToImage("image/png", quality)
+ text, textErr := vhs.TextCanvas.CanvasToImage("image/png", quality)
+ if textErr == nil && cursorErr == nil {
+ if err := os.WriteFile(
+ filepath.Join(vhs.Options.Video.Input, fmt.Sprintf(cursorFrameFormat, counter)),
+ cursor,
+ os.ModePerm,
+ ); err != nil {
+ log.Printf("error writing cursor frame: %v", err)
+ }
+ if err := os.WriteFile(
+ filepath.Join(vhs.Options.Video.Input, fmt.Sprintf(textFrameFormat, counter)),
+ text,
+ os.ModePerm,
+ ); err != nil {
+ log.Printf("error writing text frame: %v", err)
+ }
+ } else {
+ log.Printf("error: %v, %v", textErr, cursorErr)
+ }
+ }
 }
 
 // ResumeRecording indicates to VHS that the recording should be resumed.