Improvements to page turning

Reverted to an earlier page turning strategy, but with a new optimization.
Turning a page, a single time, should feel effortless and smooth. Most of all it
should not distract from reading. Before sometimes there was grinding (the
feeling that the computer was struggling). On another attempt it felt jerky or
uneven. With the new setup, the page can always be displayed and then any other
work follows.

Added refreshSpreads command
Reduced time wasted in printLoaded()
Ensure never trying to render a partially loaded spread
Added trace routines to better time function execution

cmd/cbxv/main.go

@@ -13,27 +13,37 @@ import (
 
 const (
     NAME    = "cbxv"
-    VERSION = "0.4.9"
+    VERSION = "0.5.0"
 )
 
 // Update listens for messages on the message channel and
 // handles messages by invoking messageHandlers
 func update(m *model.Model, u *ui.UI, msgChan chan util.Message, msgHandlers *MessageHandlerList) {
     for msg := range msgChan {
         msgHandler := msgHandlers.List[msg.TypeName]
+
+        // If spreads are nil, the list below are the only commands
+        // that are allowed to run
         if m.Spreads == nil &&
             (msg.TypeName != "quit" &&
             msg.TypeName != "openFile" &&
             msg.TypeName != "openFileResult" &&
             msg.TypeName != "toggleFullscreen") {
             continue
         }
+
+        // We have a handler, schedule it to run on event dispatch thread
         if msgHandler != nil {
             u.RunFunc(func() {
                 msgHandler(msg.Data)
-                u.Render(m)
             })
         }
+
+        // Render after every command, except refreshSpreads
+        if msg.TypeName != "refreshSpreads" {
+            u.Render(m)
+        }
+
         runtime.GC()
 
         // Handling the quit message above 

cmd/cbxv/messagehandlers.go

@@ -32,9 +32,6 @@ func NewMessageHandlers(m *model.Model, u *ui.UI) *MessageHandlerList {
         if m.SpreadIndex < len(m.Spreads)-1 {
             m.SpreadIndex++
             m.PageIndex = m.Spreads[m.SpreadIndex].VersoPage()
-            if !m.SpreadLoaded(m.SpreadIndex) {
-                m.RefreshSpreads()
-            }
         } else {
             handlers.List["nextFile"]("")
         }
@@ -44,9 +41,6 @@ func NewMessageHandlers(m *model.Model, u *ui.UI) *MessageHandlerList {
         if m.SpreadIndex > 0 {
             m.SpreadIndex--
             m.PageIndex = m.Spreads[m.SpreadIndex].VersoPage()
-            if !m.SpreadLoaded(m.SpreadIndex) {
-                m.RefreshSpreads()
-            }
         } else {
             handlers.List["previousFile"]("")
         }
@@ -292,7 +286,13 @@ func NewMessageHandlers(m *model.Model, u *ui.UI) *MessageHandlerList {
     }
 
     handlers.List["render"] = func(data string) {
-        //noop render always gets called after cmd
+        // noop render always gets called after cmd
+    }
+
+    // Unless it's refreshSpreads, this is the one cmd that
+    // after running we don't call render
+    handlers.List["refreshSpreads"] = func(data string) {
+        m.RefreshSpreads()
     }
 
     handlers.List["quit"] = func(data string) {

internal/model/model.go

@@ -678,18 +678,20 @@ func (m *Model) checkSpreads() {
 
 // dbg
 func (m *Model) printLoaded() {
-    var buf string
-    for i := range m.Pages {
-        if !m.Pages[i].Loaded {
-            buf += "0"
-        } else {
-            if i == m.PageIndex {
-                buf += "_"
+    if util.DEBUG == true {
+        var buf string
+        for i := range m.Pages {
+            if !m.Pages[i].Loaded {
+                buf += "0"
             } else {
-                buf += "1"
+                if i == m.PageIndex {
+                    buf += "_"
+                } else {
+                    buf += "1"
+                }
             }
         }
+        util.Log("%s\n", buf)
     }
-    util.Log("%s\n", buf)
 }
 

internal/ui/commands.go

@@ -44,12 +44,14 @@ func NewCommands(m *model.Model, u *UI) *CommandList {
 		[]uint{gdk.KEY_d, gdk.KEY_Right, gdk.KEY_l},
 		func(args ...any) {
 			u.SendMessage(util.Message{TypeName: "rightPage"})
+            u.SendMessage(util.Message{TypeName: "refreshSpreads"})
 		}))
 
 	AddCommand(cmds, NewCommand("leftPage", "Left Page",
 		[]uint{gdk.KEY_a, gdk.KEY_Left, gdk.KEY_h},
 		func(args ...any) {
 			u.SendMessage(util.Message{TypeName: "leftPage"})
+            u.SendMessage(util.Message{TypeName: "refreshSpreads"})
 		}))
 
 	AddCommand(cmds, NewCommand("firstPage", "First Page",

internal/ui/pageview.go

@@ -131,12 +131,14 @@ func (v *PageView) initRenderer(m *model.Model) {
         }
 
         spread := m.Spreads[m.SpreadIndex]
-        if m.LayoutMode == model.TWO_PAGE {
-            s := newTwoPageSpread(m, canvas, cr, spread)
-            renderTwoPageSpread(s)
-        } else if m.LayoutMode == model.ONE_PAGE {
-            s := newOnePageSpread(canvas, cr, spread.Pages[0])
-            renderOnePageSpread(s)
+        if m.SpreadLoaded(m.SpreadIndex) {
+            if m.LayoutMode == model.TWO_PAGE {
+                s := newTwoPageSpread(m, canvas, cr, spread)
+                renderTwoPageSpread(s)
+            } else if m.LayoutMode == model.ONE_PAGE {
+                s := newOnePageSpread(canvas, cr, spread.Pages[0])
+                renderOnePageSpread(s)
+            }
         }
         w := v.hud.GetAllocatedWidth() - 40
         v.hdrControl.container.SetSizeRequest(w, 8)

internal/util/util.go

@@ -682,3 +682,12 @@ func Log(format string, a ...any) {
     }
 }
 
+func TrcStart (s string) (string, time.Time) {
+    return s, time.Now() 
+}
+
+func TrcEnd (s string, startTime time.Time) {
+    endTime := time.Now() 
+    fmt.Printf("Name:%s, Time:%d\n", s, endTime.Sub(startTime).Milliseconds())
+}
+