TAV: better initial q-index prediction for target bitrate mode

assets/disk0/tvdos/include/playgui.mjs

@@ -0,0 +1,178 @@
+// Common GUI for media player
+// Created by CuriousTorvald on 2025-09-30.
+
+// Subtitle display functions
+function clearSubtitleArea() {
+    // Clear the subtitle area at the bottom of the screen
+    // Text mode is 80x32, so clear the bottom few lines
+    let oldFgColour = con.get_color_fore()
+    let oldBgColour = con.get_color_back()
+
+    con.color_pair(255, 255)  // transparent to clear
+
+    // Clear bottom 4 lines for subtitles
+    for (let row = 28; row <= 31; row++) {
+        con.move(row, 1)
+        for (let col = 1; col <= 80; col++) {
+            print(" ")
+        }
+    }
+
+    con.color_pair(oldFgColour, oldBgColour)
+}
+
+function getVisualLength(line) {
+    // Calculate the visual length of a line excluding formatting tags
+    let visualLength = 0
+    let i = 0
+
+    while (i < line.length) {
+        if (i < line.length - 2 && line[i] === '<') {
+            // Check for formatting tags and skip them
+            if (line.substring(i, i + 3).toLowerCase() === '<b>' ||
+                line.substring(i, i + 3).toLowerCase() === '<i>') {
+                i += 3  // Skip tag
+            } else if (i < line.length - 3 &&
+                      (line.substring(i, i + 4).toLowerCase() === '</b>' ||
+                       line.substring(i, i + 4).toLowerCase() === '</i>')) {
+                i += 4  // Skip closing tag
+            } else {
+                // Not a formatting tag, count the character
+                visualLength++
+                i++
+            }
+        } else {
+            // Regular character, count it
+            visualLength++
+            i++
+        }
+    }
+
+    return visualLength
+}
+
+function displayFormattedLine(line) {
+    // Parse line and handle <b> and <i> tags with colour changes
+    // Default subtitle colour: yellow (231), formatted text: white (254)
+
+    let i = 0
+    let inBoldOrItalic = false
+
+    // insert initial padding block
+    con.color_pair(0, 255)
+    con.prnch(0xDE)
+    con.color_pair(231, 0)
+
+    while (i < line.length) {
+        if (i < line.length - 2 && line[i] === '<') {
+            // Check for opening tags
+            if (line.substring(i, i + 3).toLowerCase() === '<b>' ||
+                line.substring(i, i + 3).toLowerCase() === '<i>') {
+                con.color_pair(254, 0)  // Switch to white for formatted text
+                inBoldOrItalic = true
+                i += 3
+            } else if (i < line.length - 3 &&
+                      (line.substring(i, i + 4).toLowerCase() === '</b>' ||
+                       line.substring(i, i + 4).toLowerCase() === '</i>')) {
+                con.color_pair(231, 0)  // Switch back to yellow for normal text
+                inBoldOrItalic = false
+                i += 4
+            } else {
+                // Not a formatting tag, print the character
+                print(line[i])
+                i++
+            }
+        } else {
+            // Regular character, print it
+            print(line[i])
+            i++
+        }
+    }
+
+    // insert final padding block
+    con.color_pair(0, 255)
+    con.prnch(0xDD)
+    con.color_pair(231, 0)
+}
+
+function displaySubtitle(text, position = 0) {
+    if (!text || text.length === 0) {
+        clearSubtitleArea()
+        return
+    }
+
+    // Set subtitle colours: yellow (231) on black (0)
+    let oldFgColour = con.get_color_fore()
+    let oldBgColour = con.get_color_back()
+    con.color_pair(231, 0)
+
+    // Split text into lines
+    let lines = text.split('\n')
+
+    // Calculate position based on subtitle position setting
+    let startRow, startCol
+    // Calculate visual length without formatting tags for positioning
+    let longestLineLength = lines.map(s => getVisualLength(s)).sort().last()
+
+    switch (position) {
+        case 2: // center left
+        case 6: // center right
+        case 8: // dead center
+            startRow = 16 - Math.floor(lines.length / 2)
+            break
+        case 3: // top left
+        case 4: // top center
+        case 5: // top right
+            startRow = 2
+            break
+        case 0: // bottom center
+        case 1: // bottom left
+        case 7: // bottom right
+        default:
+            startRow = 31 - lines.length
+            startRow = 31 - lines.length
+            startRow = 31 - lines.length  // Default to bottom center
+    }
+
+    // Display each line
+    for (let i = 0; i < lines.length; i++) {
+        let line = lines[i].trim()
+        if (line.length === 0) continue
+
+        let row = startRow + i
+        if (row < 1) row = 1
+        if (row > 32) row = 32
+
+        // Calculate column based on alignment
+        switch (position) {
+            case 1: // bottom left
+            case 2: // center left
+            case 3: // top left
+                startCol = 1
+                break
+            case 5: // top right
+            case 6: // center right
+            case 7: // bottom right
+                startCol = Math.max(1, 78 - getVisualLength(line) - 2)
+                break
+            case 0: // bottom center
+            case 4: // top center
+            case 8: // dead center
+            default:
+                startCol = Math.max(1, Math.floor((80 - longestLineLength - 2) / 2) + 1)
+                break
+        }
+
+        con.move(row, startCol)
+
+        // Parse and display line with formatting tag support
+        displayFormattedLine(line)
+    }
+
+    con.color_pair(oldFgColour, oldBgColour)
+}
+
+exports = {
+    clearSubtitleArea,
+    displaySubtitle
+}