Add the ability to select a source image to use in the code.

experimental/webtry/DESIGN.md

 Design
 ======
 
 
 Overview
 --------
 Allows trying out Skia code in the browser.
 
 
 Security
@@ skipping 115 matching lines @@
 
 To connect to the database from the skia-webtry-b server:
 
     $ mysql --host=173.194.83.52 --user=root --password
 
 Initial setup of the database, the user, and the only table:
 
     CREATE DATABASE webtry;
     USE webtry;
     CREATE USER 'webtry'@'%' IDENTIFIED BY '<password is in valentine>';
-    GRANT SELECT, INSERT, UPDATE ON webtry.webtry       TO 'webtry'@'%';
-    GRANT SELECT, INSERT, UPDATE ON webtry.workspace    TO 'webtry'@'%';
-    GRANT SELECT, INSERT, UPDATE ON webtry.workspacetry TO 'webtry'@'%';
+    GRANT SELECT, INSERT, UPDATE ON webtry.webtry        TO 'webtry'@'%';
+    GRANT SELECT, INSERT, UPDATE ON webtry.workspace     TO 'webtry'@'%';
+    GRANT SELECT, INSERT, UPDATE ON webtry.workspacetry  TO 'webtry'@'%';
+    GRANT SELECT, INSERT, UPDATE ON webtry.source_images TO 'webtry'@'%';
 
     // If this gets changed also update the sqlite create statement in webtry.go.
 
     CREATE TABLE webtry (
-      code      TEXT      DEFAULT ''                 NOT NULL,
-      create_ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP  NOT NULL,
-      hash      CHAR(64)  DEFAULT ''                 NOT NULL,
-      PRIMARY KEY(hash)
+      code               TEXT      DEFAULT ''                 NOT NULL,
+      create_ts          TIMESTAMP DEFAULT CURRENT_TIMESTAMP  NOT NULL,
+      hash               CHAR(64)  DEFAULT ''                 NOT NULL,
+      source_image_id    INTEGER   DEFAULT 0                  NOT NULL,
+      PRIMARY KEY(hash),
+
+      FOREIGN KEY (source) REFERENCES sources(id)
     );
 
     CREATE TABLE workspace (
       name      CHAR(64)  DEFAULT ''                 NOT NULL,
       create_ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP  NOT NULL,
-      PRIMARY KEY(name)
+      PRIMARY KEY(name),
     );
 
     CREATE TABLE workspacetry (
-      name      CHAR(64)  DEFAULT ''                 NOT NULL,
-      create_ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP  NOT NULL,
-      hash      CHAR(64)  DEFAULT ''                 NOT NULL,
-      hidden    INTEGER   DEFAULT 0                  NOT NULL,
+      name             CHAR(64)  DEFAULT ''                 NOT NULL,
+      create_ts        TIMESTAMP DEFAULT CURRENT_TIMESTAMP  NOT NULL,
+      hash             CHAR(64)  DEFAULT ''                 NOT NULL,
+      source_image_id  INTEGER   DEFAULT 0                  NOT NULL,
+      hidden           INTEGER   DEFAULT 0                  NOT NULL,
 
-      FOREIGN KEY (name) REFERENCES workspace(name)
+      FOREIGN KEY (name)   REFERENCES workspace(name),
     );
 
+    CREATE TABLE source_images (
+      id        INTEGER     PRIMARY KEY                NOT NULL,
+      image     MEDIUMBLOB  DEFAULT ''                 NOT NULL, -- Stored as PNG.
+      width     INTEGER     DEFAULT 0                  NOT NULL,
+      height    INTEGER     DEFAULT 0                  NOT NULL,
+      create_ts TIMESTAMP   DEFAULT CURRENT_TIMESTAMP  NOT NULL,
+      hidden    INTEGER     DEFAULT 0                  NOT NULL
+    );
+
+    ALTER TABLE webtry       ADD COLUMN source_image_id INTEGER DEFAULT 0 NOT NULL AFTER hash;
+    ALTER TABLE workspacetry ADD COLUMN source_image_id INTEGER DEFAULT 0 NOT NULL AFTER hash;
+
 Common queries webtry.go will use:
 
     INSERT INTO webtry (code, hash) VALUES('int i = 0;...', 'abcdef...');
 
     SELECT code, create_ts, hash FROM webtry WHERE hash='abcdef...';
 
     SELECT code, create_ts, hash FROM webtry ORDER BY create_ts DESC LIMIT 2;
 
     // To change the password for the webtry sql client:
     SET PASSWORD for 'webtry'@'%' = PASSWORD('<password is in valentine>');
 
     // Run before and after to confirm the password changed:
     SELECT Host, User, Password FROM mysql.user;
 
 Common queries for workspaces:
 
     SELECT hash, create_ts FROM workspace ORDER BY create_ts DESC;
 
     INSERT INTO workspace (name, hash) VALUES('autumn-river-12354', 'abcdef...');
 
     SELECT name FROM workspace GROUP BY name;
 
+Common queries for sources:
+
+    SELECT id, image, width, height, create_ts FROM source_images ORDER BY create_ts DESC LIMIT 100;
+
 Password for the database will be stored in the metadata instance, if the
 metadata server can't be found, i.e. running locally, then a local sqlite
 database will be used. To see the current password stored in metadata and the
 fingerprint:
 
     gcutil  --project=google.com:skia-buildbots    getinstance skia-webtry-b
 
 To set the mysql password that webtry is to use:
 
     gcutil  --project=google.com:skia-buildbots   setinstancemetadata skia-webtry-b --metadata=password:'[mysql client webtry password]' --fingerprint=[some fingerprint]
 
 To retrieve the password from the running instance just GET the right URL from
 the metadata server:
 
     curl "http://metadata/computeMetadata/v1/instance/attributes/password" -H "X-Google-Metadata-Request: True"
 
 N.B. If you need to change the MySQL password that webtry uses, you must change
 it both in MySQL and the value stored in the metadata server.
 
+Source Images
+-------------
+
+For every try the user can select an optional source image to use as an input.
+The id of the source image is just an integer and is stored in the database
+along with the other try information, such as the code.
+
+The actual image itself is also stored in a separate table, 'sources', in the
+database.  On startup we check that all the images are available in 'inout',
+and write out the images if not. Since they are all written to 'inout' we can
+use the same /i/ image handler to serve them.
+
+When a user uploads an image it is decoded and converted to PNG and stored
+as a binary blob in the database.
+
+The bitmap is available to user code as a module level variable:
+
+    SkBitmap source;
+
+The bitmap is read, decoded and stored in source before the seccomp jail is
+instantiated.
+
+
 Squid
 -----
 
 Squid is configured to run on port 80 and run as an accelerator for the actual
 Go program which is running on port 8000. The config for the squid proxy is
 held in sys/webtry_squid, which is copied into place during installation and
 squid is kept running via monit.
 
 Workspaces
 ----------
@@ skipping 14 matching lines @@
   * clike.js       - C-like syntax highlighting support
 
 Alternatively, we may consider pulling CM as an external dependency at some
 point.
 
 Installation
 ------------
 See the README file.