Scratch File Format (1.4)/User-class Objects

This article or section documents something not included in the current version of Scratch (3.0). It is only useful from a historical perspective.

This is part of a technical description of the file format.

User-class objects are Objects which can change their attributes between Scratch versions — such as stage and Sprite. For example, the attribute for "lists" was only added in a later version.

Structure

• classID: one byte describing the type of object.
• version: the version of the object, used to determine the value and type of the fields.
• length: how many fields the object has (as this may change between versions).
• fields: length number of fields (Inline Values and Object References).

Technical details

In Scratch's Squeak source code, each User-class Object implements the instance methods storeFieldsOn:, initFromFieldsFrom:version:, and fieldsVersion (found under the object i/o category). Inspecting these methods shows what fields on these objects are serialised.

(When the serialization format of an object is changed, the methods storeFieldsOn: and initFromFieldsFrom:version: are changed, and the version number returned by objStreamVersion is increased by one.)

Each User-class object can have a maximum of 255 fields.

List of User-class Objects

Some of the classes inherit from others. All Morphs inherit the properties of a Morph, for example. Inherited/superclass fields are serialised to the file before subclass fields.

Morphic-related

100 Morph

bounds, owner, submorphs, color, flags, properties

Base class for most UserObjects.

101 BorderedMorph

inherits Morph

borderWidth, borderColor

102 RectangleMorph

inherits BorderedMorph

103 EllipseMorph

inherits BorderedMorph

104 AlignmentMorph

inherits RectangleMorph

orientation, centering, hResizing, vResizing, inset

105 StringMorph

inherits Morph

font with size, emphasis, contents

106 UpdatingStringMorph

inherits StringMorph

107 SimpleSliderMorph

inherits BorderedMorph

slider, value, setValueSelector, sliderShadow, sliderColor, descending, model, target, actionSelector, arguments, actWhen

108 SimpleButtonMorph

inherits RectangleMorph

target, actionSelector, arguments, actWhen

109 SampledSound

envelopes, scaledVol, initialCount, samples, originalSamplingRate, samplesSize, scaledIncrement, scaledInitialIndex

110 ImageMorph

inherits Morph

form, transparency

111 SketchMorph

inherits Morph

originalForm, rotationCenter, rotationDegrees, rotationStyle, scalePoint, offsetWhenRotated

Scratch-specific classes

ScriptableScratchMorph

inherits Morph

objName, vars, blocksBin, isClone, media, costume

Contains methods for scripting.

123 SensorBoardMorph

inherits Morph

unknown

124 ScratchSpriteMorph

inherits ScriptableScratchMorph

visibility, scalePoint, rotationDegrees, rotationStyle, volume, tempoBPM, draggable, sceneStates, lists

A Sprite object.

125 ScratchStageMorph

inherits ScriptableScratchMorph

zoom, hPan, vPan, obsoleteSavedState, sprites, volume, tempoBPM, sceneStates, lists

The project stage. Sprites are stored as an attribute. The stage is the root object of the Object Table in Sprite files and project file contents.

140 ChoiceArgMorph

inherits Morph

Unused.

141 ColorArgMorph

inherits Morph

Unused.

142 ExpressionArgMorph

inherits Morph

Unused.

145 SpriteArgMorph

inherits Morph

Unused.

147 BlockMorph

inherits Morph

isSpecialForm, oldColor

Unused.

148 CommandBlockMorph

inherits BlockMorph

commandSpec, argMorphs, titleMorph, receiver, selector, isReporter, isTimed, wantsName, wantsPossession

Unused.

149 CBlockMorph

inherits Morph

Unused.

151 HatBlockMorph

inherits Morph

Unused.

153 ScratchScriptsMorph

inherits BorderedMorph

Unused.

154 ScratchSliderMorph

inherits Morph

Unused.

155 WatcherMorph

inherits AlignmentMorph

titleMorph, readout, readoutFrame, scratchSlider, watcher, isSpriteSpecific, unused, sliderMin, sliderMax, isLarge

A variable watcher.

157 SetterBlockMorph

inherits Morph

Unused.

158 EventHatMorph

inherits Morph

Unused.

160 VariableBlockMorph

inherits CommandBlockMorph

isBoolean

Unused.

ScratchMedia

mediaName

162 ImageMedia

inherits ScratchMedia

form, rotationCenter, textBox, jpegBytes, compositeForm

163 MovieMedia

inherits ScratchMedia

fileName, fade, fadeColor, zoom, hPan, vPan, msecsPerFrame, currentFrame, moviePlaying

Unused.

164 SoundMedia

inherits ScratchMedia

originalSound, volume, balance, compressedSampleRate, compressedBitsPerSample, compressedData

165 KeyEventHatMorph

inherits Morph

Unused.

166 BooleanArgMorph

inherits Morph

Unused.

167 EventTitleMorph

inherits Morph

Unused.

168 MouseClickEventHatMorph

inherits Morph

Unused.

169 ExpressionArgMorphWithMenu

inherits Morph

Unused.

170 ReporterBlockMorph

inherits Morph

Unused.

171 MultilineStringMorph

inherits Morph

Unused.

172 ToggleButton

inherits SimpleButtonMorph

Unused.

173 WatcherReadoutFrameMorph

inherits BorderedMorph

Unused.

174 WatcherSliderMorph

inherits SimpleSliderMorph

Unused.

175 ScratchListMorph

inherits BorderedMorph

listName, cellMorphs, target

A List object. List items are found in the cellMorphs attribute.

176 ScrollingStringMorph

inherits Morph

Unused.