2 files changed, 30 insertions, 0 deletions
diff --git a/ext/bg/js/api.js b/ext/bg/js/api.js
index f768e6f9..94a70c34 100644
--- a/ext/bg/js/api.js
+++ b/ext/bg/js/api.js
@@ -241,3 +241,32 @@ function apiFrameInformationGet(sender) {
     const frameId = sender.frameId;
     return Promise.resolve({frameId});
 }
+
+function apiInjectStylesheet(css, sender) {
+    if (!sender.tab) {
+        return Promise.reject(new Error('Invalid tab'));
+    }
+
+    const tabId = sender.tab.id;
+    const frameId = sender.frameId;
+    const details = {
+        code: css,
+        runAt: 'document_start',
+        cssOrigin: 'user',
+        allFrames: false
+    };
+    if (typeof frameId === 'number') {
+        details.frameId = frameId;
+    }
+
+    return new Promise((resolve, reject) => {
+        chrome.tabs.insertCSS(tabId, details, () => {
+            const e = chrome.runtime.lastError;
+            if (e) {
+                reject(new Error(e.message));
+            } else {
+                resolve();
+            }
+        });
+    });
+}
diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index 453f4282..c1216d95 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -185,6 +185,7 @@ Backend.messageHandlers = {
     screenshotGet: ({options}, sender) => apiScreenshotGet(options, sender),
     forward: ({action, params}, sender) => apiForward(action, params, sender),
     frameInformationGet: (params, sender) => apiFrameInformationGet(sender),
+    injectStylesheet: ({css}, sender) => apiInjectStylesheet(css, sender)
 };
 
 window.yomichan_backend = new Backend();