Add the File > Export dialog and PNG/JPG downloading (#629)

* Add export dialog

* Code review changes

* More code review feedback

* Fix compilation on stable Rust

* Fixes to problems

Co-authored-by: Keavon Chambers <keavon@keavon.com>

editor/src/frontend/frontend_message.rs

@@ -27,6 +27,7 @@ pub enum FrontendMessage {
 	TriggerFontLoadDefault,
 	TriggerIndexedDbRemoveDocument { document_id: u64 },
 	TriggerIndexedDbWriteDocument { document: String, details: FrontendDocumentDetails, version: String },
+	TriggerRasterDownload { document: String, name: String, mime: String, size: (f64, f64) },
 	TriggerTextCommit,
 	TriggerTextCopy { copy_text: String },
 	TriggerViewportResize,

editor/src/frontend/utility_types.rs

@@ -31,6 +31,41 @@ pub enum MouseCursorIcon {
 
 impl Default for MouseCursorIcon {
 	fn default() -> Self {
-		Self::Default
+		MouseCursorIcon::Default
+	}
+}
+
+#[derive(Clone, Copy, Debug, Eq, Deserialize, PartialEq, Serialize)]
+pub enum FileType {
+	Svg,
+	Png,
+	Jpg,
+}
+
+impl Default for FileType {
+	fn default() -> Self {
+		FileType::Svg
+	}
+}
+
+impl FileType {
+	pub fn to_mime(self) -> &'static str {
+		match self {
+			FileType::Svg => "image/svg+xml",
+			FileType::Png => "image/png",
+			FileType::Jpg => "image/jpeg",
+		}
+	}
+}
+
+#[derive(Clone, Copy, Debug, Eq, Deserialize, PartialEq, Serialize)]
+pub enum ExportBounds {
+	AllArtwork,
+	Artboard(LayerId),
+}
+
+impl Default for ExportBounds {
+	fn default() -> Self {
+		ExportBounds::AllArtwork
 	}
 }