feat: translate subtitles with an OpenAI-compatible LLM

src/qml/Main.qml

@@ -19,12 +19,22 @@ Kirigami.ApplicationWindow {
         id: player
         initialUrl: root.initialUrl
         onAboutRequested: root.pageStack.layers.push(aboutPage)
+        onSettingsRequested: root.pageStack.layers.push(settingsPage)
         onFullScreenToggled: root.visibility = root.visibility === Window.FullScreen ? Window.Windowed : Window.FullScreen
     }
 
     pageStack.globalToolBar.style: Kirigami.ApplicationHeaderStyle.ToolBar
     pageStack.columnView.columnResizeMode: Kirigami.ColumnView.SingleColumn
 
+    onClosing: QtPotatoSettings.save()
+
+    Component {
+        id: settingsPage
+        SettingsPage {
+            translator: player.translator
+        }
+    }
+
     Component {
         id: aboutPage
         FormCard.AboutPage {}

src/qml/PlayerPage.qml

@@ -10,8 +10,10 @@ Kirigami.Page {
 
     property url initialUrl
     readonly property alias mediaTitle: mpv.mediaTitle
+    readonly property alias translator: translator
 
     signal aboutRequested()
+    signal settingsRequested()
     signal fullScreenToggled()
 
     title: KI18n.i18nc("@title", "Player")
@@ -31,6 +33,13 @@ Kirigami.Page {
             shortcut: "F"
             onTriggered: page.fullScreenToggled()
         },
+        Kirigami.Action {
+            icon.name: "configure"
+            text: KI18n.i18nc("@action", "Settings")
+            displayHint: Kirigami.DisplayHint.AlwaysHide
+            shortcut: StandardKey.Preferences
+            onTriggered: page.settingsRequested()
+        },
         Kirigami.Action {
             icon.name: "help-about"
             text: KI18n.i18nc("@action", "About QtPotato")
@@ -83,6 +92,25 @@ Kirigami.Page {
         mpv.showText(KI18n.i18nc("@info:osd", "Subtitle delay: %1 ms", Math.round(delay * 1000)))
     }
 
+    TranslationService {
+        id: translator
+        onTranslated: (subtitleUrl, fromCache) => {
+            mpv.showSecondarySubtitleFile(subtitleUrl,
+                KI18n.i18nc("@item:inlistbox subtitle track, %1 is a language", "%1 (translated)", QtPotatoSettings.targetLanguage))
+            mpv.showText(fromCache
+                ? KI18n.i18nc("@info:osd", "Loaded the saved translation")
+                : KI18n.i18nc("@info:osd", "Translation ready"))
+        }
+    }
+
+    Connections {
+        target: mpv
+        // A translation belongs to the file it was started for.
+        function onCurrentUrlChanged() {
+            translator.cancel()
+        }
+    }
+
     function isSubtitleFile(url: url): bool {
         return /\.(srt|ass|ssa|vtt|sub|sup)$/i.test(url.toString())
     }
@@ -212,6 +240,8 @@ Kirigami.Page {
                         id: subtitlePopup
                         objectName: "subtitlePopup"
                         mpv: mpv
+                        translator: translator
+                        onSettingsRequested: page.settingsRequested()
                         x: subtitleButton.width - width
                         y: -height - Kirigami.Units.smallSpacing
                     }

src/qml/SettingsPage.qml

@@ -0,0 +1,132 @@
+import QtQuick
+import QtQuick.Controls as QQC2
+import QtQuick.Layouts
+import org.kde.kirigami as Kirigami
+import org.kde.kirigamiaddons.formcard as FormCard
+import org.kde.ki18n
+
+FormCard.FormCardPage {
+    id: page
+
+    required property TranslationService translator
+
+    title: KI18n.i18nc("@title", "Settings")
+
+    // Fields write to the settings object as they change; this writes it to disk.
+    Component.onDestruction: QtPotatoSettings.save()
+
+    Kirigami.InlineMessage {
+        Layout.fillWidth: true
+        Layout.topMargin: Kirigami.Units.largeSpacing
+        Layout.leftMargin: Kirigami.Units.largeSpacing
+        Layout.rightMargin: Kirigami.Units.largeSpacing
+        type: Kirigami.MessageType.Error
+        text: page.translator.errorText || ApiKeyStore.error
+        visible: text.length > 0
+        showCloseButton: true
+        onVisibleChanged: if (!visible) page.translator.clearError()
+    }
+
+    FormCard.FormHeader {
+        title: KI18n.i18nc("@title:group", "Subtitle Translation")
+    }
+
+    FormCard.FormCard {
+        FormCard.FormTextFieldDelegate {
+            label: KI18n.i18nc("@label:textbox", "API base URL")
+            placeholderText: "https://example.com/v1"
+            text: QtPotatoSettings.apiBaseUrl
+            inputMethodHints: Qt.ImhUrlCharactersOnly | Qt.ImhNoAutoUppercase
+            onTextEdited: QtPotatoSettings.apiBaseUrl = text.trim()
+        }
+
+        FormCard.FormDelegateSeparator {}
+
+        FormCard.FormPasswordFieldDelegate {
+            id: apiKeyField
+            label: KI18n.i18nc("@label:textbox", "API key")
+            placeholderText: ApiKeyStore.hasKey
+                ? KI18n.i18nc("@info:placeholder", "Saved in the wallet. Type a new key to replace it.")
+                : KI18n.i18nc("@info:placeholder", "Not set")
+            onEditingFinished: {
+                if (text.trim().length > 0) {
+                    ApiKeyStore.setKey(text)
+                    text = ""
+                }
+            }
+        }
+
+        FormCard.FormButtonDelegate {
+            visible: ApiKeyStore.hasKey
+            icon.name: "edit-delete-remove"
+            text: KI18n.i18nc("@action:button", "Remove Saved API Key")
+            onClicked: ApiKeyStore.setKey("")
+        }
+
+        FormCard.FormDelegateSeparator {}
+
+        FormCard.FormComboBoxDelegate {
+            id: modelCombo
+
+            // Swapping the list makes the combo box jump to its first entry; that must
+            // not overwrite the model the user chose.
+            property bool updatingList: false
+
+            function showModels() {
+                const chosen = QtPotatoSettings.model
+                updatingList = true
+                model = page.translator.availableModels
+                currentIndex = page.translator.availableModels.indexOf(chosen)
+                editText = chosen
+                updatingList = false
+            }
+
+            text: KI18n.i18nc("@label:listbox", "Model")
+            editable: true
+            onEditTextChanged: if (!updatingList) QtPotatoSettings.model = editText.trim()
+            Component.onCompleted: showModels()
+
+            Connections {
+                target: page.translator
+                function onAvailableModelsChanged() {
+                    modelCombo.showModels()
+                }
+            }
+        }
+
+        FormCard.FormButtonDelegate {
+            icon.name: "view-refresh"
+            text: page.translator.fetchingModels
+                ? KI18n.i18nc("@action:button", "Loading Models…")
+                : KI18n.i18nc("@action:button", "Load Models from the API")
+            description: page.translator.availableModels.length > 0
+                ? KI18n.i18ncp("@info", "%1 model available", "%1 models available", page.translator.availableModels.length)
+                : ""
+            enabled: !page.translator.fetchingModels
+            onClicked: page.translator.fetchModels()
+        }
+
+        FormCard.FormDelegateSeparator {}
+
+        FormCard.FormTextFieldDelegate {
+            label: KI18n.i18nc("@label:textbox", "Translate into")
+            text: QtPotatoSettings.targetLanguage
+            onTextEdited: QtPotatoSettings.targetLanguage = text.trim()
+        }
+
+        FormCard.FormDelegateSeparator {}
+
+        FormCard.FormSpinBoxDelegate {
+            label: KI18n.i18nc("@label:spinbox", "Lines per request")
+            from: 5
+            to: 200
+            stepSize: 5
+            value: QtPotatoSettings.batchSize
+            onValueModified: QtPotatoSettings.batchSize = value
+        }
+    }
+
+    FormCard.FormSectionText {
+        text: KI18n.i18nc("@info", "Works with any OpenAI-compatible API. The whole subtitle track is translated in batches before it is shown, and the result is kept so the same track is never translated twice.")
+    }
+}

src/qml/SubtitlePopup.qml

@@ -9,6 +9,11 @@ QQC2.Popup {
     id: popup
 
     required property MpvItem mpv
+    required property TranslationService translator
+
+    signal settingsRequested()
+
+    readonly property var currentTrack: mpv.subtitleTracks.find(track => track.id === mpv.subtitleId) ?? null
 
     // [{ id, text }] with "Off" first, shared by both track pickers.
     readonly property var trackModel: [{ id: 0, text: KI18n.i18nc("@item:inlistbox no subtitle", "Off") }]
@@ -98,6 +103,70 @@ QQC2.Popup {
             text: KI18n.i18nc("@action:button", "Load Subtitle File…")
             onClicked: subtitleDialog.open()
         }
+
+        Kirigami.Separator {
+            Kirigami.FormData.isSection: true
+            Kirigami.FormData.label: KI18n.i18nc("@title:group", "Translation")
+        }
+
+        QQC2.Button {
+            visible: !popup.translator.busy
+            enabled: popup.currentTrack !== null
+            icon.name: "translate"
+            text: KI18n.i18nc("@action:button", "Translate Subtitle into %1", QtPotatoSettings.targetLanguage)
+            onClicked: popup.translator.translate(popup.mpv.currentUrl, popup.currentTrack, popup.mpv.mediaTitle)
+
+            QQC2.ToolTip.text: KI18n.i18nc("@info:tooltip", "Translates the subtitle chosen above and shows the result as the secondary subtitle")
+            QQC2.ToolTip.visible: hovered
+            QQC2.ToolTip.delay: Kirigami.Units.toolTipDelay
+        }
+
+        RowLayout {
+            visible: popup.translator.busy
+            Layout.preferredWidth: Kirigami.Units.gridUnit * 16
+            spacing: Kirigami.Units.smallSpacing
+
+            QQC2.ProgressBar {
+                Layout.fillWidth: true
+                from: 0
+                to: 1
+                value: popup.translator.progress
+                indeterminate: popup.translator.progress === 0
+            }
+
+            QQC2.ToolButton {
+                icon.name: "dialog-cancel"
+                text: KI18n.i18nc("@action:button", "Cancel translation")
+                display: QQC2.AbstractButton.IconOnly
+                onClicked: popup.translator.cancel()
+
+                QQC2.ToolTip.text: text
+                QQC2.ToolTip.visible: hovered
+                QQC2.ToolTip.delay: Kirigami.Units.toolTipDelay
+            }
+        }
+
+        QQC2.Label {
+            visible: popup.translator.busy
+            text: popup.translator.statusText
+        }
+
+        Kirigami.InlineMessage {
+            Layout.preferredWidth: Kirigami.Units.gridUnit * 22
+            type: Kirigami.MessageType.Error
+            text: popup.translator.errorText
+            visible: text.length > 0
+            showCloseButton: true
+            onVisibleChanged: if (!visible) popup.translator.clearError()
+            actions: Kirigami.Action {
+                icon.name: "configure"
+                text: KI18n.i18nc("@action:button", "Settings")
+                onTriggered: {
+                    popup.close()
+                    popup.settingsRequested()
+                }
+            }
+        }
     }
 
     FileDialog {