feat(msi): give a template its own cabinet for per-customer files

Rebranding recompressed the whole ~100MB payload because one cabinet held
everything. In template mode preprocess.py puts the handful of files a custom
client replaces on a second cabinet, so a patch rebuilds a few hundred KB and
leaves the payload cabinet alone. The shipped msi is built without template
mode and keeps its single cabinet.

The branding assets need conditional components. A stock build ships none of
them -- there is no icon.ico, icon.png or logo*.png, only icon.svg -- so the
template has to carry placeholders for the File rows to exist, and a customer
supplies whichever they want. Installing a placeholder unconditionally would
give a customer with no logo a placeholder image, where today a missing asset
means no logo at all: the client tries each candidate and treats the failure as
absence. So each optional asset installs only when its property says the
customer supplied one.

CI creates those placeholders and builds the template with the new mode.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Q7fBdTwziR5BHTkSz7Tzcm

.github/workflows/flutter-build.yml

@@ -405,6 +405,11 @@ jobs:
         # it also names payload that must never be renamed, such as librustdesk.dll
         # and drivers\RustDeskPrinterDriver.
         #
+        # --template also puts the files a custom client replaces in their own
+        # cabinet, so rebranding rebuilds a few hundred KB rather than recompressing
+        # the whole payload. The shipped msi above is built without it and is
+        # unaffected.
+        #
         # Building the arm64 template on the native arm64 runner is what makes ARM
         # custom clients possible at all: the build agents are x64 and cannot run
         # preprocess.py against an ARM exe.
@@ -413,8 +418,18 @@ jobs:
           git checkout -- res/msi
           cp -r ./rustdesk ./rustdesk-msi-template
           mv ./rustdesk-msi-template/rustdesk.exe ./rustdesk-msi-template/RDAPPNAM.exe
+          # A stock build ships none of the files a custom client replaces, so the
+          # template needs a placeholder for each to have a File row to patch. The
+          # branding assets install only when the patcher says the customer supplied
+          # one, so an unused placeholder is never installed.
+          Set-Content -Path ./rustdesk-msi-template/custom.txt -Value 'placeholder' -NoNewline
+          $assets = './rustdesk-msi-template/data/flutter_assets/assets'
+          New-Item -ItemType Directory -Force -Path $assets | Out-Null
+          foreach ($a in 'icon.ico','icon.png','logo.png','logo_light.png','logo_dark.png') {
+            Set-Content -Path "$assets/$a" -Value 'placeholder' -NoNewline
+          }
           pushd ./res/msi
-          python preprocess.py --arp -d ../../rustdesk-msi-template --app-name RDAPPNAM
+          python preprocess.py --arp --template -d ../../rustdesk-msi-template --app-name RDAPPNAM
           $msiPlatform = if ('${{ matrix.job.arch }}' -eq 'aarch64') { 'ARM64' } else { 'x64' }
           msbuild msi.sln -t:clean -p:Configuration=Release -p:Platform=$msiPlatform
           msbuild msi.sln -p:Configuration=Release -p:Platform=$msiPlatform /p:TargetVersion=Windows10

res/msi/Package/Package.wxs

@@ -13,6 +13,12 @@
 		<PropertyRef Id="AddRemovePropertiesFile" />
 
 		<Media Id="1" Cabinet="cab1.cab" EmbedCab="yes" CompressionLevel="high" />
+		<!--$Media2Start$-->
+		<!-- preprocess.py in template mode adds a second cabinet here, holding only
+		     the files that differ per customer, so a custom client can be produced by
+		     rebuilding that small cabinet instead of the whole package. The shipped
+		     msi is built without template mode and keeps a single cabinet. -->
+		<!--$Media2End$-->
 		<Icon Id="AppIcon" SourceFile="Resources\icon.ico" />
 
 		<!-- User Interface -->

res/msi/preprocess.py

@@ -65,6 +65,14 @@ def make_parser():
     parser.add_argument(
         "-c", "--custom", action="store_true", help="Is custom client", default=False
     )
+    parser.add_argument(
+        "--template",
+        action="store_true",
+        default=False,
+        help="Build a template to be patched per customer rather than a finished "
+        "package: puts the files a custom client replaces in their own cabinet, so "
+        "rebranding rebuilds a few hundred KB instead of the whole payload.",
+    )
     parser.add_argument(
         "--conn-type",
         type=str,
@@ -90,6 +98,43 @@ def make_parser():
     return parser
 
 
+# Files a custom client replaces. Kept in their own cabinet by --template so that
+# rebranding rebuilds a few hundred KB instead of recompressing the whole payload.
+# The app executable is handled separately: it has its own component in RustDesk.wxs.
+#
+# A template has to ship a placeholder for each of these so there is a File row to
+# patch, but the branding assets are optional for a customer and a stock build has
+# none of them at all. So each optional one installs only when its property is set,
+# which the patcher does for the files a customer actually supplied. Otherwise a
+# customer without a logo would install the placeholder, where today they get no
+# logo at all -- the client treats a missing asset as "no logo".
+PER_CUSTOMER_DISK_ID = 2
+PER_CUSTOMER_FILES = {
+    # relative path -> property gating installation, or None if always installed
+    "custom.txt": None,
+    "data/flutter_assets/assets/icon.ico": "CC_HAS_ICON_ICO",
+    "data/flutter_assets/assets/icon.png": "CC_HAS_ICON_PNG",
+    "data/flutter_assets/assets/logo.png": "CC_HAS_LOGO",
+    "data/flutter_assets/assets/logo_light.png": "CC_HAS_LOGO_LIGHT",
+    "data/flutter_assets/assets/logo_dark.png": "CC_HAS_LOGO_DARK",
+}
+
+
+def normalize_relative(relative_path):
+    path = relative_path.replace("\\", "/")
+    while path.startswith("./"):
+        path = path[2:]
+    return path.lower()
+
+
+def is_per_customer(relative_path):
+    return normalize_relative(relative_path) in PER_CUSTOMER_FILES
+
+
+def per_customer_condition(relative_path):
+    return PER_CUSTOMER_FILES.get(normalize_relative(relative_path))
+
+
 def read_lines_and_start_index(file_path, tag_start, tag_end):
     with open(file_path, "r", encoding="utf-8") as f:
         lines = f.readlines()
@@ -110,7 +155,7 @@ def read_lines_and_start_index(file_path, tag_start, tag_end):
     return lines, index_start
 
 
-def insert_components_between_tags(lines, index_start, app_name, dist_dir):
+def insert_components_between_tags(lines, index_start, app_name, dist_dir, template=False):
     indent = g_indent_unit * 3
     path = Path(dist_dir)
     idx = 1
@@ -124,12 +169,23 @@ def insert_components_between_tags(lines, index_start, app_name, dist_dir):
             if subdir != ".":
                 dir_attr = f'Subdirectory="{subdir}"'
 
+            relative = file_path.relative_to(path).as_posix()
+            disk_attr = ""
+            condition_attr = ""
+            if template and is_per_customer(relative):
+                disk_attr = f' DiskId="{PER_CUSTOMER_DISK_ID}"'
+                # Branding assets are optional, and the template only carries a
+                # placeholder, so install one only when the customer supplied it.
+                condition = per_customer_condition(relative)
+                if condition:
+                    condition_attr = f' Condition="{condition} = 1"'
+
             # Don't generate Component Id and File Id like 'Component_{idx}' and 'File_{idx}'
             # because it will cause error
             # "Error WIX0130	The primary key 'xxxx' is duplicated in table 'Directory'"
             to_insert_lines = f"""
-{indent}<Component Guid="{uuid.uuid4()}" {dir_attr}>
+{indent}<Component Guid="{uuid.uuid4()}" {dir_attr}{condition_attr}>
-{indent}{g_indent_unit}<File Source="{file_path.as_posix()}" KeyPath="yes" Checksum="yes" />
+{indent}{g_indent_unit}<File Source="{file_path.as_posix()}" KeyPath="yes" Checksum="yes"{disk_attr} />
 {indent}</Component>
 """
             lines.insert(index_start + 1, to_insert_lines[1:])
@@ -138,17 +194,52 @@ def insert_components_between_tags(lines, index_start, app_name, dist_dir):
     return True
 
 
-def gen_auto_component(app_name, dist_dir):
+def gen_auto_component(app_name, dist_dir, template=False):
     return gen_content_between_tags(
         "Package/Components/RustDesk.wxs",
         "<!--$AutoComonentStart$-->",
         "<!--$AutoComponentEnd$-->",
         lambda lines, index_start: insert_components_between_tags(
-            lines, index_start, app_name, dist_dir
+            lines, index_start, app_name, dist_dir, template
         ),
     )
 
 
+def gen_media2():
+    """Second cabinet holding only what a custom client replaces."""
+
+    def func(lines, index_start):
+        indent = g_indent_unit * 2
+        lines.insert(
+            index_start + 1,
+            f'{indent}<Media Id="{PER_CUSTOMER_DISK_ID}" Cabinet="cab2.cab"'
+            ' EmbedCab="yes" CompressionLevel="high" />\n',
+        )
+        return lines
+
+    return gen_content_between_tags(
+        "Package/Package.wxs", "<!--$Media2Start$-->", "<!--$Media2End$-->", func
+    )
+
+
+def put_app_exe_on_media2():
+    """The app executable has its own component, so it is moved by name."""
+    target = Path(sys.argv[0]).parent.joinpath("Package/Components/RustDesk.wxs")
+    with open(target, "r", encoding="utf-8") as f:
+        content = f.read()
+    old = '<File Id="App.exe" Name="$(var.Product).exe" KeyPath="yes" Checksum="yes">'
+    new = (
+        '<File Id="App.exe" Name="$(var.Product).exe" KeyPath="yes" Checksum="yes"'
+        f' DiskId="{PER_CUSTOMER_DISK_ID}">'
+    )
+    if content.count(old) != 1:
+        print(f"Error: expected exactly one App.exe File element, found {content.count(old)}")
+        return False
+    with open(target, "w", encoding="utf-8") as f:
+        f.write(content.replace(old, new))
+    return True
+
+
 def gen_pre_vars(args, dist_dir):
     def func(lines, index_start):
         upgrade_code = uuid.uuid5(uuid.NAMESPACE_OID, app_name + ".exe")
@@ -537,7 +628,13 @@ if __name__ == "__main__":
     if not gen_conn_type(args):
         sys.exit(-1)
 
-    if not gen_auto_component(app_name, dist_dir):
+    if args.template:
+        if not gen_media2():
+            sys.exit(-1)
+        if not put_app_exe_on_media2():
+            sys.exit(-1)
+
+    if not gen_auto_component(app_name, dist_dir, args.template):
         sys.exit(-1)
 
     if not gen_custom_dialog_bitmaps():