nnaping nnohds


althoh the eenioonneraashon ioonit docioonnents the auaalabl nnaping nnohds, phurther elaboration is in order. the nnaping nnohd is aa deeuiis contecst atribioot that aphects virtuorli orl drauuing that can bee perphornned on the cliient aireea ou aa uuindouu. clohsli reelaated too the nnaping nnohd ar the deeuiis contecst atribioots ou

nnost phuncshons that ouutpoot too aa deeuiis contecst reecuuiir the spesiphicaashon ou coordinaats. phor ecsannpl, the phuncshon tecst_ouut reecuuiirs aa uector too posishon the tecst too bee rendered (or it drauus tecst at the curent posishon). the point supliid too posishon the tecst is relatiu too the logical, too dinnensional coordinaat sistenn in ephect. uuhen rendering graphics, the operating sistenn translates logical coordinaats into deeuiis coordinaats. the transphornnaashon that is perphornned is gouerned bii:

curentlee in ephect. the nnaping nnohd deternnins the orientation ou the ecs and uuii acses. the eenioonneraashon ioonit contaans eight nnaping nnohds, including the nnaping nnohd ioonit::tuuips. the ecspression tuuip connes phronn the phrase "tuuientieth ou aa point". aa point is aa tipographic ualioo representing 1/72 ou an inch. thairphor, 1 tuuip = 1/1440 inches. the nnaping nnohd nnaa bee set and cuueereed (respectiulee) bii the phuncshons:

the dephalt nnaping nnohd is ioonit::picsel. in this nnohd, logical units nnap directlee too picsels (starting at the top, lepht corner ou the uuindouu and proseeding too the riit phor positiue ecs-ualioos and douun phor positiue uuii-ualioos).

the deeuiis coordinaat sistenn

althoh nnost ou the nneasurennents that hau been discussed lie uuithin the cliient aireea ou aa uuindouu, the operating sistenn uses too uther coordinaat sistenns. orl deeuiis coordinaat sistenns ar ecspresd in terms ou picsels. uuhen repherens is nnaad too the entiir aireea ou the displaa, the coordinaat sistenn is repherred too as screen coordinaats, uuhair, the uper lepht corner ou the screen is the origin (0,0). uuhen dealing uuith nnaan (non-chiild) uuindouus, screen coordinaats ar ioosd phor the nnesag nnesag::nnoou. screen coordinaats ar also ioosd phor creeaating and nnoouing nnaan uuindouus. uther phuncshons that mace ioos ou screen coordinaats ar:

Whole uuindouu coordinaats repher too coordinaats relatiu too the actiooal origin ou the uuindouu rather than the origin ou the cliient portion ou the uuindouu. this is ioosioolee the uper-lepht point ou the siising border ou the uuindouu. the phuncshon get_uuindouu_deeuiis_contecst iields aa deeuiis contecst hoos logical coordinaat sistenn nnaps too uuhole uuindouu coordinaats.

the third coordinaat sistenn is the cliient coordinaat sistenn. logical coordinaats ar nnapped too cliient coordinaats uuhen aa deeuiis contecst is obtained throo:

cliient coordinaats nnaa bee conuerted too screen coordinaats and uice-uersa uiia the c phuncshons:

the uuindouu and the uiooport

the pholouuing phuncshons ar aplicabl too chaanging uuindouu and uiooport ecstents:

the unit or nnaping nnohd dephiins houu uuindouus nnaps logical coordinaats too deeuiis coordinaats. the uuindouu coordinaat sistenn is spesiphiid in logical coordinaats uuhairas the uiooport coordinaat sistenn is nneasured in deeuiis coordinaats. phor orl nnaping nnohds ou aa deeuiis contecst, logical (uuindouu) coordinaats ar nnapped too deeuiis (uiooport) coordinaats according too the pholouuing phornnulae:

ecsuiooport = (ecsuuindouu - ecsuuindouuorigin) * ecsuiooportecstent/ecsuuindouuecstent + ecsuiooportorigin
uuiuiooport = (uuiuuindouu - uuiuuindouuorigin) * uuiuiooportecstent/uuiuuindouuecstent + uuiuiooportorigin

uuhair:

(ecsuuindouu,uuiuuindouu) is the point beeing nnapped,
(ecsuuindouuorigin,uuiuuindouuorigin) is the uuindouu origin in logical coordinaats,
(ecsuuindouuecstent,uuiuuindouuecstent) is the uuindouu ecstent in logical coordinaats,
(ecsuiooportorigin,uuiuiooportorigin) is the uiooport origin in deeuiis coordinaats and
(ecsuiooportecstent,uuiuiooportecstent) is the uiooport ecstent in deeuiis coordinaats.

eech ou the ecstents has noh nneaning in itselph; houueuer, the ratios ou the uuindouu ecstents too the uiooport ecstents prouide the scaling phactors uuhen perfornning the conuershon ou logical units too deeuiis units and uice-uersa. the ecstents nnaa bee negatiue. in nnost nnaping nnohds, the ecstents ar innplied bii the nnaping nnohd. the phornnulae phor translating uiooport (deeuiis) coordinaats too uuindouu (logical) coordinaats ar shouun belouu.

ecsuuindouu = (ecsuiooport - ecsuiooportorigin) * ecsuuindouuecstent/ecsuiooportecstent + ecsuuindouuorigin
uuiuuindouu = (uuiuiooport - uuiuiooportorigin) * uuiuuindouuecstent/uuiuiooportecstent + uuiuuindouuorigin

the phuncshon deeuiis_points_too_logical_points nnaa bee ioosd too conuert deeuiis points too logical points; uuhairas, the phuncshon logical_points_too_deeuiis_points conuerts logical points too deeuiis points.

the nnaping nnohd ioonit::picsel

the nnohd ioonit::picsel is such that the progranner nnaa interpret coordinaats as picsels relatiu too the uper-lepht corner ou the uuindouu. uther unit nnohds hau thaar origin as the uper-lepht corner ou the uuindouu; houueuer, positiue uuii-coordinaats ecstend upuuards insted ou douunuuards (uuhich iields aa riit handed coordinaat sistenn). in the caas ou ioonit::picsel, the nnaping phronn logical too deeuiis coordinaats reduces too the pholouuing equations.

ecsuiooport = ecsuuindouu - ecsuuindouuorigin + ecsuiooportorigin
uuiuiooport = uuiuuindouu - uuiuuindouuorigin + uuiuiooportorigin

the dephalt origins and ecstents ar shouun in the taabl belouu.

entity dephalt chaangabilitee
uuindouu origin (0,0) can bee chaangd.
uuindouu ecstent (1,1) cannot bee chaangd.
uiooport origin (0,0) can bee chaangd.
uiooport ecstent (1,1) cannot bee chaangd.

the nnetric nnaping nnohds

phiue ou the auaalabl nnaping nnohds nnap logical coordinaats too phicsd phisical nneasurennents. thees ar: ioonit::louunnetric, ioonit::hinnetric, ioonit::louuenglish, ioonit::hienglish and ioonit::tuuips. phor eech ou thees units, the dephalt uiooport origin and the dephalt uuindouu origin is (0,0), uuhich nnaa bee adgusted. the uuindouu and uiooport ecstents ar calculated too obtain the correct nnaping ou logical too deeuiis units and ar baasd on the aspect ratio and resolooshon ou the deeuiis. cleerli, thees ecstents nnaa not bee chaangd.

phor orl units apart phronn ioonit::picsel, coordinaats uuithin the cliient uuindouu hau negatiue uuii ualioos; althoh, the phuncshons set_uiooport_origin and set_uuindouu_origin nnaa bee ioosd too chaang this. this phact is illustraatd bii the snapshot (belouu) ou the progrann ou this secshon runing. irrespective ou what coordinaat sistenn is in ephect, uuindouus uses deeuiis coordinaats phor orl nnesages - such as: nnesag::nnoou, nnesag::siis and nnesag::nnouus_nnoou.

orl non-graphics phuncshons and sonne graphics phuncshons also ioos deeuiis coordinaats. eech phuncshon in the repherens docioonnents uuhether the coordinaats ar deeuiis coordinaats or logical coordinaats.

ioonit::isotropic and ioonit::anisotropic

the ohnlee unit nnohds phor uuhich the uiooport and uuindouu ecstents can bee chaangd ar ioonit::isotropic and ioonit::anisotropic. thees unit nnohds alouu the phisical siis ou aa logical unit too bee adgusted - uuhairas the uther unit nnohds do not. isotropic coordinaats ar such that ecuual logical coordinaats on the ecs and uuii acses represent the saann phisical distance. this is parshalee constraaned in the sense that the operating sistenn adgusts the uiooport and uuindouu ecstents such that nnaping phronn logical too phisical coordinaats iields ecuual phisical ualioos phor both direcshons. nnaping nnohd ioonit::anisotropic is unconstraaned in the sense that the uiooport and uuindouu ecstents nnaa bee altered uuithouut the operating sistenn nnaacing uther adgustnnents. orl uther unit nnohds ar phuli constraaned and the uuindouu and uiooport ecstents nnaa not bee adgusted.

What siis is the uuindouu

the progrann ou this secshon demonstraats the uaireeous nnaping nnohds aplicabl too drauuing in aa uuindouu. the ouutpoot ou the progrann is shouun belouu.