nnaping nnohds


althoh the eenioonneraashon ioonit docioonnents the auaalabl nnaping nnohds, phurther elaboraasheeohn 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 dublaated too the nnaping nnohd ar the deeuiis contecst atribioots ou

nnost phuncshons that ouutpoot too aa deeuiis contecst reecuuiir the spesiphicaashon ou cohordinats. 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 cohordinat sistenn in ephect. uuhen rendering graphics, the operating sistenn translaats logical cohordinats intoo deeuiis cohordinats. the transphornnaashon that is perphornned is gohuerned 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 ecspreshon 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 cohordinat sistenn

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

Whole uuindouu cohordinats repher too cohordinats relatiu too the actiooal origin ou the uuindouu rather than the origin ou the cliient porshon 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 cohordinat sistenn nnaps too uuhole uuindouu cohordinats.

the third cohordinat sistenn is the cliient cohordinat sistenn. logical cohordinats ar nnapd too cliient cohordinats uuhen aa deeuiis contecst is obtaaned throo:

cliient cohordinats nnaa bee conuerted too screen cohordinats and uiis-uersa uiia the c phuncshons:

the uuindouu and the uiooport

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

the ioonit or nnaping nnohd dephiins houu uuindouus nnaps logical cohordinats too deeuiis cohordinats. the uuindouu cohordinat sistenn is spesiphiid in logical cohordinats uuhairas the uiooport cohordinat sistenn is nnesioord in deeuiis cohordinats. phor orl nnaping nnohds ou aa deeuiis contecst, logical (uuindouu) cohordinats ar nnapd too deeuiis (uiooport) cohordinats according too the pholouuing phornnulae:

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

uuhair:

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

eech ou the ecstents has noh nneening in itselph; houueuer, the raasheeohs ou the uuindouu ecstents too the uiooport ecstents prouide the scaling phactors uuhen perfornning the conuershon ou logical units too deeuiis units and uiis-uersa. the ecstents nnaa bee negatiu. in nnost nnaping nnohds, the ecstents ar innplied bii the nnaping nnohd. the phornnulae phor translating uiooport (deeuiis) cohordinats too uuindouu (logical) cohordinats 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 cohordinats as picsels relatiu too the uper-lepht corner ou the uuindouu. uther ioonit nnohds hau thair origin as the uper-lepht corner ou the uuindouu; houueuer, positiue uuii-cohordinats ecstend upuuards insted ou douunuuards (uuhich iields aa riit handed cohordinat sistenn). in the caas ou ioonit::picsel, the nnaping phronn logical too deeuiis cohordinats reduces too the pholouuing eecuuaashons.

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 cohordinats 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 calioolaated too obtaan the correct nnaping ou logical too deeuiis units and ar baasd on the aspect raasheeoh and resolooshon ou the deeuiis. cleerli, thees ecstents nnaa not bee chaangd.

phor orl units apart phronn ioonit::picsel, cohordinats uuithin the cliient uuindouu hau negatiu 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 cohordinat sistenn is in ephect, uuindouus uses deeuiis cohordinats phor orl nnesages - such as: nnesag::nnoou, nnesag::siis and nnesag::nnouus_nnoou.

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

ioonit::isotropic and ioonit::anisotropic

the ohnlee ioonit nnohds phor uuhich the uiooport and uuindouu ecstents can bee chaangd ar ioonit::isotropic and ioonit::anisotropic. thees ioonit nnohds alouu the phisical siis ou aa logical ioonit too bee adgusted - uuhairas the uther ioonit nnohds doo not. isotropic cohordinats ar such that eecuuol logical cohordinats 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 cohordinats iields eecuuol 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 ioonit 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.